A milecastle was a small fort (fortlet), a rectangular fortification built during the period of the Roman Empire. They were placed at intervals of approximately one Roman mile along several major frontiers, for example Hadrian's Wall in Great Britain, hence the name.
Pons Aelius, or Newcastle Roman Fort, was an auxiliary castra and small Roman settlement on Hadrian's Wall in the Roman province of Britannia Inferior, situated on the north bank of the River Tyne close to the centre of present-day Newcastle upon Tyne, and occupied between the 2nd and 4th centuries AD.
Milecastle 4 (Westgate Road) was a milecastle of the Roman Hadrian's Wall. Its remains exist beneath the Newcastle Arts Centre at 67-75 Westgate Road. This position is some way away from its predicted position which is at these coordinates: 54.970440°N 1.608669°W The actual location is between the predicted positions of Turrets 4A and 4B, which has led to suggestions that the numbering and positioning of milecastles and turrets on this part of Hadrian's Wall should be reconsidered.
The Vallum is a huge earthwork associated with Hadrian's Wall in England. Unique on any Roman frontier, it runs practically from coast to coast to the south of the wall. It was built a few years after the wall. Current opinion is that the Vallum demarcated the southern boundary of a military zone, bounded on the north by the wall.
Milecastle 3 (Ouseburn) was a milecastle of the Roman Hadrian's Wall. No remains exist, but it was thought to have been located at the junction of the A187 Byker Bridge and Stephen Street.
Milecastle 1 (Stott's Pow) was a milecastle of the Roman Hadrian's Wall. It was located near the (now disappeared) valley of Stott's Pow. Its remains are covered over, and are located beneath the recreation ground at Miller's Dene. Early excavations and investigations of Turret 0B were mistakenly interpreted as Milecastle 1. The Milecastle sits within the parish of Wallsend.
Milecastle 2 (Walker) was a milecastle of the Roman Hadrian's Wall. No remains are currently visible, having been built over, but its probable location is at or near the junction of the A187 Fossway and Tunstall Avenue, in the parish of Wallsend.
Milecastle 5 (Quarry House) was the first milecastle west of Pons Aelius fort of the Roman Hadrian's Wall. No remains exist of the milecastle, though its supposed position is at the junction of the A186 Westgate road and the B1311 Corporation Street. No remains currently exist.
Milecastle 8 (West Denton) was a milecastle of the Roman Hadrian's Wall. Its remains are located in West Denton, Newcastle upon Tyne. The milecastle has two associated turret structures that are known as turret 8A and turret 8B. The turrets and milecastle were excavated in the 1920s, yielding some pottery and stone carvings, and have since been overlain by modern roads. The exact location of the structures is disputed, with the road hiding any surface traces. The Milecastle forms part of the Hadrian's Wall World Heritage Site.
Milecastle 9 (Chapel House) was a milecastle of the Roman Hadrian's Wall. Its remains exist partially as a low platform, and are located in West Denton (to the west of Newcastle upon Tyne), 300 yards (270 m) from Chapel House Farm. However, the northern part of the remains are now mostly covered by the modern roads (A69/B6528). The milecastle marks a watershed between those with relatively well-defined positions (to the west) and those whose position are less certain (to the east).
Milecastle 13 (Rudchester Burn) was a milecastle of the Roman Hadrian's Wall. Its remains exist as a low platform south of the B6318 Military Road.
Milecastle 21 (Down Hill) was a milecastle of the Roman Hadrian's Wall. The site was identified by measurement only, as the milecastle's remains have been totally removed. This is probably due to extensive quarrying at the site, which now lies under pasture (and partly beneath the Military Road).
Milecastle 22 (Portgate) was a milecastle of the Roman Hadrian's Wall. Its remains exist as a low, turf covered platform just east of the Portgate roundabout (junction of the A68 and B6318). The platform is 0.5 metres (1.6 ft) on the east side, reducing to only a parch mark on the west side.
Milecastle 23 (Stanley) was a milecastle of the Roman Hadrian's Wall. Its remains exist as a low, grass covered platform with traces of an external ditch (as Milecastle 25). It is located to the south of the B6318 Military Road around 1.5 kilometres (0.93 mi) west of its junction with the A68.
Pike Hill Signal Tower was one of a number of signal stations that were built on high ground overlooking the line of the Roman Stanegate road in northern Britannia during the early 2nd century. It later became incorporated into Hadrian's Wall. Its remains, a 2-metre long fragment of the south-east wall, lie south of a modern road cutting and field wall, located in the parish of Waterhead in Cumberland, United Kingdom. The tower is located between Turret 51B and Turret 52A with the fort of Banna located to the east.
Milecastle 27 (Low Brunton) was a milecastle of the Roman Hadrian's Wall. It was located on the line of Hadrian's Wall, approximately midway between the A6079 and the River North Tyne. Its remains survive as a slight squarish platform with a maximum height of 0.4 metres (1.3 ft), but it is poorly defined to the north and east.
Milecastle 25 (Codlawhill) was a milecastle of the Roman Hadrian's Wall. Its remains exist as a low platform, and are located to the south of the B6318 Military Road (about 1 metre (3.3 ft) high), nearly 5 kilometres (3.1 mi) to the west of its junction with the A68.
Milecastle 29 (Tower Tye) was a milecastle of the Roman Hadrian's Wall. Its remains exist as a mutilated earth platform accentuated by deep robber-trenches around all sides, and are located beside the B6318 Military Road. Like Milecastles 9, 23, 25, and 51, a ditch has been identified around the Milecastle, and is still visible to a small extent. It has been postulated that this was as a result of the need for drainage on the site.
Milecastle 32 (Carraw) was a milecastle of the Roman Hadrian's Wall. Its remains exist as earthworks and with no exposed masonry. The layout of the milecastle walls is defined (still quite evident) by robber trenches (to a maximum depth of 0.3 metres (1 ft 0 in). The north wall is beneath a modern wall.
Milecastle 34 (Grindon) was a milecastle of the Roman Hadrian's Wall. There are no visible remains, but the site is within a small, tree-filled, walled enclosure located around 0.5 kilometres (0.31 mi) east of Sewingshields farm.
Ancient Romeportal 
