Squatting on a headland above gorgeous Trecastle Bay, 2 miles south of the village, Barclodiad y Gawres (the Giantess' Apronful) is the largest neolithic tomb in Wales. When it was excavated in the 1950s, archaeologists were excited to find five standing stones inside, decorated in spirals and zigzags similar to those found in Ireland's Boyne Valley, along with the cremated remains of two men.
Due to problems with vandalism, the entrance to the mound is now blocked by an iron gate, but you can still peer into the murky space. If you're keen to get inside, call into Wayside Stores in Llanfaelog (1 mile up the road) to make an appointment between noon and 4pm on Saturdays, Sundays and bank holidays, and the staff will send someone down to open up.