The River Rhondda is a river in South Wales with two major tributaries, Rhondda Fawr and Rhondda Fach.
Mynydd Machen or Machen Mountain 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-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.
Penmoelallt or Onllwyn is a hill in the northern part of the county borough of Rhondda Cynon Taff in south Wales. It lies within the Brecon Beacons National Park and Fforest Fawr Geopark. To its east lies the deep valley of Cwm Taf and to its north a rather shallower valley in which the Nant Cadlan originates. To the west is the hill known as Mynydd-y-glog and to the south are slopes draining into the River Taff and the Afon Cynon. The hill culminates in a broken plateau with several knolls rising above the 420m contour. Its afforested nature makes it difficult to determine the precise location of its highest point but this probably lies somewhere around OS grid ref SO 003096. Older maps indicate a spot height of 1376 ft above sea level at SO 000090.
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.
Cefn Manmoel is the name given to the broad ridge of high ground between the Sirhowy Valley and Ebbw Vale in the Valleys region of South Wales. It straddles the boundary between the unitary areas of Caerphilly and Blaenau Gwent.
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.
Mynydd Bedwellte is the name given to the broad ridge of high ground between the Rhymney Valley and the Sirhowy Valley in the Valleys region of South Wales. It straddles the boundary of the unitary areas of Caerphilly and Blaenau Gwent.
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.
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.
Mynydd Meio is a 322-metre-high hill in the county borough of Caerphilly in South Wales. Parts of its western slopes fall within Rhondda Cynon Taf county borough. Its eastern slopes drop away to Cwm yr Aber between Caerphilly and Abertridwr and its western slopes to the valley of the Taf. The high point is just over 200 m north of the trig point which sits at 322 metres (1,056 ft) above sea-level.
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.
Cefn Gwyngul is a long broad ridge to the east of the Rhondda Fach valley in Rhondda Cynon Taf County Borough in South Wales. Its 470m high summit is marked by an ancient cairn known as Carn-y-Pigwn, on which is a more recent trig point. Much of the hill is cloaked by modern forestry plantations though its southwestern flank between Porth and Ferndale has not been coniferised. The earthworks of a Roman camp remain on the ridge at OS grid ref ST 002982.
Mynydd Twyn-glas is a sprawling 472-metre-high mountain extending into Caerphilly and Torfaen county boroughs in South Wales. It lies southwest of Pontypool, west of Cwmbran and east of Newbridge and taking the form of a rolling plateau the margins of which are defined by steep slopes, many of which are cloaked with conifer plantations. A broad shoulder extending south from the summit is known as Mynydd Maen whilst to the north is Mynydd Llwyd. The thickly afforested northern slopes of the hill drop down steeply into Cwm y Glyn.
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. The current name is a possible corruption of Mynydd y Llan, referencing the parish church of St Tudor, situated on its plateau. the church site has been occupied since the 5th century, with an early British site, being replaced by the Norman 11th century church.
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 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 landslide eastern side which rises above the Swansea Valley, drainage on this side flowing to the River Tawe.
