Coity Mountain is a flat-topped mountain in the South Wales Valleys, between Blaenavon and Abertillery. The highest points of both Torfaen and Blaenau Gwent unitary authorities are at the summit of Coity Mountain. The summit is also known as Twyn Ffynhonnau Goerion. Some 2 km (1 mi) to the southeast lies a major subsidiary top of the hill, Mynydd Varteg Fawr (549m) at the southeastern end of whose broad ridge is a trig point at 544m. A few hundred metres to the southeast of this summit is a memorial known as the "Dog Stone" which commemorates Carlo the Red Setter, a dog shot accidentally by his master while hunting on the 12 August 1864. Co-ordinates for the Dog Stone 51.45'15.58N 3.05'08.81W. Other notable tops include those of Mulfran (524m) which overlooks the town of Brynmawr and Mynydd James immediately east of the town of Blaina.
Pen y Gadair Fawr is an 800 metres (2,625 ft) high subsidiary summit of Waun Fach and the second highest peak in the Black Mountains in south-eastern Wales. Marked by a medium-sized cairn, it is a much more distinguished top than its parent 1.5 km to the northwest. Its 658 metres (2,159 ft) high top Pen Twyn Mawr is about 2 km to the southeast.
Mynydd Machen is a 362-metre-high (1,188 ft) hill lying between the town of Risca and the village of Machen in Caerphilly County Borough in south Wales. Its summit is crowned by a trig point and a mast.
Mynydd Illtud is an extensive area of common land near Libanus, Powys, Wales, located in the Brecon Beacons National Park and some three miles south-west of Brecon. The common is an undulating plateau lying between 330 and 370 metres above sea level. Its highest points are 381 metres (1,250 ft) at Allt Lom and 367 metres (1,204 ft) at Twyn y Gaer trig point overlooking the valley of the River Usk. Twyn y Gaer is the site of an Iron Age hill fort.
Pen Allt-mawr is a 719 metres (2,359 ft) high subsidiary summit of Waun Fach and the third highest peak in the Black Mountains in south-eastern Wales. A very recognisable and prominent peak of the Black Mountains, it lies near the end of the more westerly of Waun Fach's two broad southern ridges. Its top Pen Twyn Glas is to the north, while its close neighbour Pen Cerrig-calch is to the south. A prominent spur 1 km to the SSW of the summit is known as Pen Gloch-y-pibwr. The stepped Bryniog ridge curves southward from this point.
Mynydd-y-glog is a hill just east of the village of Penderyn in the northern corner of the county borough of Rhondda Cynon Taff in south Wales. It lies within the Brecon Beacons National Park and Fforest Fawr Geopark. Its summit plateau rises to a height of 389m / 1277 ft at OS grid ref SN 982088, a spot marked by a trig point. To its north lies the partly dry valley of Pant Sychbant which forms the eastern extension of Cwm Cadlan. Its southern slopes are drained by various streams which feed into the Afon Cynon.
Mynydd Carn-y-cefn is the name given to the broad ridge of high ground between the Ebbw Vale and the valley of the Ebbw Fach in the Valleys region of South Wales. It lies within the unitary area of Blaenau Gwent, formerly Monmouthshire.
Mynydd Merthyr is a broad ridge of high ground between Taff Vale and the Cwm Cynon in the Valleys region of South Wales. It forms the boundary between the unitary authorities of Rhondda Cynon Taff to the west and Merthyr Tydfil to the east.
Mynydd Cilfach-yr-encil attains a height of 445m at OS grid reference SO 079033 making it the high point of the broad ridge of high ground between Taff Vale and Cwm Bargod in the Valleys region of South Wales. It lies within the unitary area of Merthyr Tydfil.
Cefn y Brithdir is the name given to the broad ridge of high ground between the Rhymney Valley and Cwm Darran in the Valleys region of South Wales. It lies within the unitary area of Caerphilly.
The geology of Monmouthshire in southeast Wales largely consists of a thick series of sedimentary rocks of different types originating in the Silurian, Devonian, Carboniferous, Triassic and Jurassic periods.
Mynydd y Drum is a hill on the border between the county of Powys and Neath Port Talbot County Borough, south Wales. The summit of the hill is in Neath Port Talbot at 298m and lies towards the western end of a broad curving ridge, the larger part of which is in Powys. The eastern half of the hill is currently being opencasted for coal. The hill is sometimes referred to simply as The Drum.
Cefn Eglwysilan is a hill in South Wales, the twin 382m summits of which lie 2 km east of Pontypridd in Rhondda Cynon Taf county borough. Its eastern side lies within the community of Aber Valley in Caerphilly county borough. Like neighbouring Mynydd Eglwysilan, the hill is named after the hamlet of Eglwysilan, the church here being dedicated to an obscure saint Ilan. A wireless transmission station is sited on the more northerly of the two summits. The southerly one is crowned by a trig point.
Mynydd Eglwysilan is a 355-metre-high hill in the Caerphilly county borough in South Wales 3 km to the south of Nelson and a similar distance southwest of Ystrad Mynach. To its south is Senghenydd at the head of the Aber Valley. Like neighbouring Cefn Eglwysilan, the hill is named after the hamlet of Eglwysilan 4 km to the southwest, the church here being dedicated to an obscure Saint Ilan. Remains of a linear earthwork known as Senghenydd Dyke stretch across the southern side of the hill. It is considered to mark the edge of an extensive 13th-century deer park associated with nearby Caerphilly Castle.
Mynydd y Gaer is a 295-metre-high hill in Bridgend County Borough in South Wales. The summit is crowned by a trig point.
Mynydd y Lan is a 381-metre-high flat-topped hill in Caerphilly county borough in South Wales. It falls largely within the community of Ynysddu but its northern and eastern margins are within Crosskeys community. Its largely wooded southern and eastern flanks rise steeply from the Sirhowy and Ebbw valleys respectively. A wireless transmission station is located towards the northern end of the summit plateau.
Mynydd y Grug is a hill lying just west of the village of Cwmfelinfach and about 4 km to the northeast of Caerphilly in Caerphilly county borough in South Wales. Its summit was formerly at a height of around 358 m, but since the top has been covered by a large spoil heap and landscaped its height has now increased to 375 m, though some authorities take other values for the summit height. A number of ancient cairns are found along its edge overlooking the Sirhowy Valley, the slopes up from which are largely wooded.
Mynydd William Meyrick is a 535-metre-high hill straddling the boundary of Bridgend and Rhondda Cynon Taf county boroughs between the valley of the Rhondda Fawr and Ogmore Valley in South Wales. It takes the form of a broad northwest-southeast ridge with numerous broad shoulders extending to the east, south and west, each of which have different names and some of which constitute minor tops. Listed clockwise from the north these are; Mynydd Maendy, Mynydd Ton, Mynydd Bwllfa, Mynydd Pwllyrhebog, Mynydd Maes-teg, Mynydd y Gwair and Mynydd yr Aber. The summit of the entire massif is often referred to as Mynydd Ton. Its western sides are open moorland whilst its eastern sides have been afforested by the Forestry Commission.
Mynydd Allt-y-grug is a 338-metre-high hill immediately west of Ystalyfera in the county borough of Neath Port Talbot in South Wales. Its twin summits are around 400m apart. The upper part of the hill is largely covered in heather whilst conifers clothe its western slopes and gorse, bracken and bramble cover much of its rough landslipped eastern side which rises above the Swansea Valley, drainage on this side flowing to the River Tawe.
Mynydd Garnclochdy is a gentle summit on the long moorland ridge which extends south from Blorenge towards Pontypool and which defines the boundary between the modern county of Monmouthshire to the east and the county borough of Torfaen to the west though historically it was entirely within the traditional county of Monmouthshire. Its summit, at a height of 448 m (1407 ft), is marked by a small cairn. The summit and the eastern slopes of the hill fall within the Brecon Beacons National Park. A southern top of the hill, Mynydd Garn-wen achieves a height of 436m, and carries a trig point further south again at an elevation of 425m. To the north the broad moorland ridge runs via a poorly defined 425m top and a col at 404m elevation just south of a minor east–west road, into Mynydd y Garn-fawr, east of Blaenavon.
