Mynydd Illtud

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 (1,080 and 1,210 ft) 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.

Like Cefn Llechid and Fforest Fach to the west, Mynydd Illtud is formed from the mudstones and sandstones of the St. Maughans Formation of the Old Red Sandstone laid down during the Devonian period. The sandstones have been quarried in places such as at Allt Lom.
The area was overrun by ice during the last ice age and evidence of this is seen in the glacial till which is spread across this undulating plateau and the occasional erratic block of sandstone. Traeth Mawr and Traeth Bach, two rock hollows towards the south-western end of the common are now filled with peat, core sections of which have proved valuable in unravelling the climatic and vegetational history of this area over the last 10,000 years.

Walkers can freely access the entire common as it is open access land, though horseriders and mountain-bikers are restricted to the minor roads, restricted byways and bridleways which criss-cross this area. Other than along the public road network there is no legal right for the public to take motor vehicles (including motorbikes) across the common. Landowners and those with commoners' rights do have certain vehicular rights over Mynydd Illtud. The Brecon Beacons Mountain Centre stands next to Mynydd Illtud on its eastern side and provides advice for visitors wishing to enjoy the area.

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