The 'hill of the old people' is a much damaged Neolithic chambered cairn now represented by a kidney-shaped mound some 40m by 30m and up to 5.0m high. It is set at the end of a saddle between two low hills or rises at the top of slopes falling to the east. A terrace or bank, about 108m long, 18m wide and up to 1.0m high, runs south across the mouth of the saddle from the mound and begins to climb the southern rise. It is balanced by a natural limestone ledge on the north side of the tomb. The complex was excavated from 1929 to 1935 and the mound has since been adapted to display the restored chamber.
The recognition of additional features from the air in 1999 prompted a resistivity survey. There are earthworks of a deserted settlement to the south of the monument, pre-dating the enhancement of Plas Newydd Park at the start of the nineteenth century (NPRN 265416). The terrace was the earliest feature and was revetted by drystone walling. A Bronze Age cinerary urn had been placed at its far end. It appears to be joined to a less substantial bank on the east to form an enclosure about 25m across, however, this lesser feature may be a plough headland.
The cairn itself had a small central chamber set behind a wide forecourt opening to the east commanding views across the Menai Strait. Bones were encountered in the chamber in about 1754. The 1929-35 excavations recovered sherds of Neolithic pottery.
Sources: Hemp in Archaeologia 85 (1935), 253-292
RCAHMW Anglesey Inventory (1937), 57
Driver & others in Antiquity 74 (2000), 761-2
Leivers & others in Archaeology in Wales 41 (2001), 3-9
John Wiles, RCAHMW, 27 July 2007.