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The moat surrounding Matsumoto Castle Matsumoto castle 3.jpg
The moat surrounding Matsumoto Castle

A moat is a deep, broad ditch, either dry or filled with water, that is dug and surrounds a castle, fortification, building or town, historically to provide it with a preliminary line of defence. In some places moats evolved into more extensive water defences, including natural or artificial lakes, dams and sluices. In older fortifications, such as hillforts, they are usually referred to simply as ditches, although the function is similar. In later periods, moats or water defences may be largely ornamental. They could also act as a sewer.


Historical use


North view of the fortress of Buhen in Ancient Egypt. Buhen3.jpg
North view of the fortress of Buhen in Ancient Egypt.

Some of the earliest evidence of moats has been uncovered around ancient Egyptian castles. One example is at Buhen, a castle excavated in Nubia. Other evidence of ancient moats is found in the ruins of Babylon, and in reliefs from ancient Egypt, Assyria, and other cultures in the region. [1] [2]

Evidence of early moats around settlements has been discovered in many archaeological sites throughout Southeast Asia, including Noen U-Loke, Ban Non Khrua Chut, Ban Makham Thae and Ban Non Wat. The use of the moats could have been either for defensive or agriculture purposes. [3]


A medieval moat castle in Steinfurt, Germany Castle moat and watermill Steinfurt.jpg
A medieval moat castle in Steinfurt, Germany

Moats were excavated around castles and other fortifications as part of the defensive system as an obstacle immediately outside the walls. In suitable locations they might be filled with water. A moat made access to the walls difficult for siege weapons such as siege towers and battering rams, which needed to be brought up against a wall to be effective. A water-filled moat made the practice of mining - digging tunnels under the castles in order to effect a collapse of the defences - very difficult as well. Segmented moats have one dry section and one section filled with water. Dry moats that cut across the narrow part of a spur or peninsula are called neck ditches . Moats separating different elements of a castle, such as the inner and outer wards, are cross ditches.

The word was adapted in Middle English from the Old French motte "mound, hillock" and was first applied to the central mound on which a castle was erected (see Motte and bailey) and then came to be applied to the excavated ring, a ‘dry moat’. The shared derivation implies that the two features were closely related and possibly constructed at the same time. [4] The term moat is also applied to natural formations reminiscent of the artificial structure and to similar modern architectural features.

Later western fortification

The 17th-century fortified town of Naarden, Netherlands, showing bastions projecting into the wet moat NIMH - 2011 - 3706 - Aerial photograph of Naarden, The Netherlands.jpg
The 17th-century fortified town of Naarden, Netherlands, showing bastions projecting into the wet moat

With the introduction of siege artillery, a new style of fortification emerged in the 16th century using low walls and projecting strong points called bastions, which was known as the trace italienne . The walls were further protected from infantry attack by wet or dry moats, sometimes in elaborate systems. [5] When this style of fortification was superseded by lines of polygonal forts in the mid-19th century, moats continued to be used for close protection. [6]


The Walls of Benin were a combination of ramparts and moats, called Iya, used as a defence of the capital Benin City in present-day Edo State of Nigeria. It was considered the largest man-made structure lengthwise, second only to the Great Wall of China and the largest earthwork in the world. Recent work by Patrick Darling has established it as the largest man-made structure in the world, larger than Sungbo's Eredo, also in Nigeria. It enclosed 6,500 km2 of community lands. Its length was over 16,000 km of earth boundaries. It was estimated that earliest construction began in 800 and continued into the mid-15th century.

The walls are built of a ditch and dike structure, the ditch dug to form an inner moat with the excavated earth used to form the exterior rampart.

The Benin Walls were ravaged by the British in 1897. Scattered pieces of the walls remain in Edo, with material being used by the locals for building purposes. The walls continue to be torn down for real-estate developments.

The Walls of Benin City were the world's largest man-made structure. Fred Pearce wrote in New Scientist:

"They extend for some 16,000 kilometres in all, in a mosaic of more than 500 interconnected settlement boundaries. They cover 6,500 square kilometres and were all dug by the Edo people. In all, they are four times longer than the Great Wall of China, and consumed a hundred times more material than the Great Pyramid of Cheops. They took an estimated 150 million hours of digging to construct, and are perhaps the largest single archaeological phenomenon on the planet."


Map of the Tokyo Imperial Palace and surrounding Gardens showing the elaborate moat system Imperial Palace Tokyo Map.png
Map of the Tokyo Imperial Palace and surrounding Gardens showing the elaborate moat system

Japanese castles often have very elaborate moats, with up to three moats laid out in concentric circles around the castle and a host of different patterns engineered around the landscape. The outer moat of a Japanese castle typically protects other support buildings in addition to the castle.

As many Japanese castles have historically been a very central part of their cities, the moats have provided a vital waterway to the city. Even in modern times the moat system of the Tokyo Imperial Palace consists of a very active body of water, hosting everything from rental boats and fishing ponds to restaurants. [7]

Most modern Japanese castles have moats filled with water, but castles in the feudal period more commonly had 'dry moats' karabori (空堀, 【からぼり】, lit. "empty moat"), a trench. A tatebori (竪堀, 【たてぼり】, lit. "vertical moat") is a dry moat dug into a slope. A unejo tatebori (畝状竪堀, lit. "furrowed shape empty moat") is a series of parallel trenches running up the sides of the excavated mountain, and the earthen wall, which was also called doi (土居, 【どい】, lit. "earth mount"), was an outer wall made of earth dug out from a moat. Even today it is common for mountain Japanese castles to have dry moats. A mizubori (水堀, 【みずぼり】, lit. "water moat") is a moat filled with water.

Moats were also used in the Forbidden City and Xi'an in China; in Vellore in India; Hsinchu in Taiwan; and in Southeast Asia, such as at Angkor Wat in Cambodia; Mandalay in Myanmar and Chiang Mai in Thailand.


The only moated fort ever built in Australia was Fort Lytton in Brisbane. As Brisbane was much more vulnerable to attack than either Sydney or Melbourne a series of coastal defences was built throughout Moreton Bay, Fort Lytton being the largest. Built between 1880 and 1881 in response to fear of a Russian invasion, it is a pentagonal fortress concealed behind grassy embankments and surrounded by a water-filled moat.

North America

Moats were developed independently by North American indigenous people of the Mississippian culture as the outer defence of some fortified villages. The remains of a 16th-century moat are still visible at the Parkin Archeological State Park in eastern Arkansas.

The Maya people also used moats, for example in the city of Becan.

European colonists in the Americas often built dry ditches surrounding forts built to protect important landmarks, harbours or cities (e.g. Fort Jay on Governors Island in New York Harbor).

Modern usage

Architectural usage

Dry moat at the James Farley Post Office in New York City. Farley dry moat jeh.JPG
Dry moat at the James Farley Post Office in New York City.

Dry moats were a key element used in French Classicism and Beaux-Arts architecture dwellings, both as decorative designs and to provide discreet access for service. Excellent examples of these can be found in Newport, Rhode Island at Miramar (mansion) and The Elms, as well as at Carolands, outside of San Francisco, California, and at Union Station in Toronto, Ontario, Canada. Additionally, a dry moat can allow light and fresh air to reach basement workspaces, as for example at the James Farley Post Office in New York City.

Anti-terrorist moats

Whilst moats are no longer a significant tool of warfare, modern architectural building design continues to use them as a defence against certain modern threats, such as terrorist attacks from car bombs and armoured fighting vehicles. For example, the new location of the Embassy of the United States in London, opened in 2018, includes a moat among its security features - the first moat built in England for more than a century. [8] Modern moats may also be used for aesthetic or ergonomic purposes.

The Catawba Nuclear Station has a concrete moat around some of the plant. (Other sides of the plant are bordering a lake.) The moat is a part of precautions added to such sites after the September 11, 2001 attacks. [9]

Safety moats

Moats, rather than fences, separate animals from spectators in many modern zoo installations. Moats were first used in this way by Carl Hagenbeck at his Tierpark in Hamburg, Germany. [10] The structure, with a vertical outer retaining wall rising direct from the moat, is an extended usage of the ha-ha of English landscape gardening.

Border defence moats

In 2004 plans were suggested for a two-mile moat across the southern border of the Gaza Strip to prevent tunnelling from Egyptian territory to the border town of Rafah. [11]

In 2008 city officials in Yuma, Arizona planned to dig out a two-mile stretch of a 180-hectare (440-acre) wetland known as Hunters Hole to control immigrants coming from Mexico. [12]

Pest control moats

Researchers of jumping spiders, which have excellent vision and adaptable tactics, [13] built water-filled miniature moats, too wide for the spiders to jump across. Some specimens were rewarded for jumping then swimming and others for swimming only. Portia fimbriata from Queensland generally succeeded, for whichever method they were rewarded. [14] When specimens from two different populations of Portia labiata were set the same task, members of one population determined which method earned them a reward, whilst members of the other continued to use whichever method they tried first and did not try to adapt. [15]

As a basic method of pest control in bonsai, a moat may be used to restrict access of crawling insects to the bonsai.

See also

Related Research Articles

<span class="mw-page-title-main">Medieval fortification</span>

Medieval fortification refers to medieval military methods that cover the development of fortification construction and use in Europe, roughly from the fall of the Western Roman Empire to the Renaissance. During this millennium, fortifications changed warfare, and in turn were modified to suit new tactics, weapons and siege techniques.

<span class="mw-page-title-main">Castle</span> Fortified residential structure of medieval Europe

A castle is a type of fortified structure built during the Middle Ages predominantly by the nobility or royalty and by military orders. Scholars debate the scope of the word castle, but usually consider it to be the private fortified residence of a lord or noble. This is distinct from a palace, which is not fortified; from a fortress, which was not always a residence for royalty or nobility; from a pleasance which was a walled-in residence for nobility, but not adequately fortified; and from a fortified settlement, which was a public defence – though there are many similarities among these types of construction. Use of the term has varied over time and has also been applied to structures such as hill forts and 19th- and 20th-century homes built to resemble castles. Over the approximately 900 years when genuine castles were built, they took on a great many forms with many different features, although some, such as curtain walls, arrowslits, and portcullises, were commonplace.

<span class="mw-page-title-main">Defensive wall</span> Fortification used to protect an area from potential aggressors

A defensive wall is a fortification usually used to protect a city, town or other settlement from potential aggressors. The walls can range from simple palisades or earthworks to extensive military fortifications with towers, bastions and gates for access to the city. From ancient to modern times, they were used to enclose settlements. Generally, these are referred to as city walls or town walls, although there were also walls, such as the Great Wall of China, Walls of Benin, Hadrian's Wall, Anastasian Wall, and the Atlantic Wall, which extended far beyond the borders of a city and were used to enclose regions or mark territorial boundaries. In mountainous terrain, defensive walls such as letzis were used in combination with castles to seal valleys from potential attack. Beyond their defensive utility, many walls also had important symbolic functions – representing the status and independence of the communities they embraced.

<span class="mw-page-title-main">Fortification</span> Military defensive construction

A fortification is a military construction or building designed for the defense of territories in warfare, and is also used to establish rule in a region during peacetime. The term is derived from Latin fortis ("strong") and facere.

<span class="mw-page-title-main">Concentric castle</span>

A concentric castle is a castle with two or more concentric curtain walls, such that the outer wall is lower than the inner and can be defended from it. The layout was square where the terrain permitted, or an irregular polygon where curtain walls of a spur castle followed the contours of a hill.

<span class="mw-page-title-main">Fort Luton</span>

Fort Luton was built between 1876 and 1892 south of Chatham, Medway, South East England. It is one of the five late Victorian land front forts built to defend the overland approaches to Chatham. It is the smallest of the Chatham forts and was built near to the village of Luton.

<span class="mw-page-title-main">Bastion fort</span> Early modern fortification style built to withstand cannon fire

A bastion fort or trace italienne is a fortification in a style that evolved during the early modern period of gunpowder when the cannon came to dominate the battlefield. It was first seen in the mid-fifteenth century in Italy. Some types, especially when combined with ravelins and other outworks, resembled the related star fort of the same era.

<span class="mw-page-title-main">Pevensey Castle</span> Castle in East Sussex, England

Pevensey Castle is a medieval castle and former Roman Saxon Shore fort at Pevensey in the English county of East Sussex. The site is a scheduled monument in the care of English Heritage and is open to visitors. Built around 290 AD and known to the Romans as Anderitum, the fort appears to have been the base for a fleet called the Classis Anderidaensis. The reasons for its construction are unclear; long thought to have been part of a Roman defensive system to guard the British and Gallic coasts against Saxon pirates, it has more recently been suggested that Anderitum and the other Saxon Shore forts were built by a usurper in an ultimately unsuccessful attempt to prevent Rome from reimposing its control over Britain.

<span class="mw-page-title-main">Counterscarp</span> Outer side of a ditch or moat in a fortification

A scarp and a counterscarp are the inner and outer sides, respectively, of a ditch or moat used in fortifications. Attackers must descend the counterscarp and ascend the scarp. In permanent fortifications the scarp and counterscarp may be encased in stone. In less permanent fortifications, the counterscarp may be lined with paling fence set at an angle so as to give no cover to the attackers but to make advancing and retreating more difficult.

<span class="mw-page-title-main">Forts in India</span>

The existence of the earliest forts in India have been substantiated by documentation and excavation. In the medieval times, the architecture of the forts had both Hindu and Muslim influence. The forts constructed by the British initially opted for simple designs. The existing castles are continually modified and many of them are privately owned.

<span class="mw-page-title-main">Aslockton Castle</span>

Aslockton Castle is a ruined fortification, a motte-and-bailey castle, in the village of Aslockton, Nottinghamshire. The original name of the settlement was Aslachetone, which suggests a possible Norse origin; it was mentioned in the Domesday Book of 1086 where it was described as a large settlement.

<span class="mw-page-title-main">Fukuoka Castle</span>

Fukuoka Castle is a Japanese castle located in Chūō-ku, Fukuoka, Japan. It is also known as Maizuru Castle or Seki Castle. Completed in the early Edo period for tozama daimyō Kuroda Nagamasa, it has been decreed a historic site by the Japanese government.

<span class="mw-page-title-main">Séré de Rivières system</span> Fortifications in France

The Séré de Rivières system was named after Raymond Adolphe Séré de Rivières, its originator. The system was an ensemble of fortifications built from 1874 along the frontiers and coasts of France. The fortresses were obsolescent by 1914 but were used during the First World War.

<span class="mw-page-title-main">Ditch (fortification)</span> Ground obstacle to slow an attacking force

In military engineering, a ditch is an obstacle designed to slow down or break up an attacking force, while a trench is intended to provide cover to the defenders. In military fortifications the side of a ditch farthest from the enemy and closest to the next line of defence is known as the scarp while the side of a ditch closest to the enemy is known as the counterscarp.

<span class="mw-page-title-main">Walls of Benin</span> Series of earthworks around present-day Benin City, Nigeria

The Walls of Benin are a series of earthworks made up of banks and ditches, called Iya in the Edo language, in the area around present-day Benin City, the capital of present-day Edo, Nigeria. They consist of 15 km (9.3 mi) of city iya and an estimated 16,000 kilometres of rural iya in the area around Benin. The 'walls' of Benin City and surrounding areas were described as "the world's largest earthworks carried out prior to the mechanical era" by the Guinness book of Records. Some estimates suggest that the walls of Benin may have been constructed between the thirteenth and mid-fifteenth century CE and others suggest that the walls of Benin may have been constructed during the first millennium CE.

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<span class="mw-page-title-main">Zwinger</span> Area between main and secondary walls of a fortification

"Zwinger" is a German word for outer ward or outer bailey. It represents an open kill zone area between two defensive walls that is used for defensive purposes. Zwingers were built in the post-classical and early modern periods to improve the defence of castles and town walls. The term is usually left untranslated, but is sometimes rendered as "outer courtyard", presumably referring to the subsequent role of a Zwinger as a castle's defences became redundant and it was converted into a palace or schloss; however, this belies its original purpose as a form of killing ground for the defence. The word is linked with zwingen, "to force", perhaps because the Zwinger forced an enemy to negotiate it before assaulting the main defensive line. Essenwein states that the "main purpose of this feature was so that the besieging force could not reach the actual castle wall very easily with battering rams or belfries, but had to stop at the lower, outer wall; also that two ranks of archers, behind and above one another, could fire upon the approaching enemy".

<span class="mw-page-title-main">Rampart (fortification)</span> Defensive bank or wall surrounding a fortified site, such as a castle or settlement

In fortification architecture, a bank or rampart is a length of embankment or wall forming part of the defensive boundary of a castle, hillfort, settlement or other fortified site. It is usually broad-topped and made of excavated earth and/or masonry.

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<span class="mw-page-title-main">Chateau des Marais, Guernsey</span>

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