Dun Port a' Chaisteil translates as bay of the fort. An iron age fort some 2,000 years old and survives as a low turf-covered enclosure set upon a rocky outcrop looking out towards the Isle of Islay from Kintyre. The interior contains a later rectangular building. The rocky knoll is near inaccessible 30 feet above the sea surrounded by water at high tide.

The dun is located very close to the busy road where there is limited space to park with care on the landward side near a small cottage and requires a short walk north, crossing a road barrier towards the shore on your left. You will need an ordnance survey map to work out which rocky knoll the dun is situated, as there are also other ancient forts to the north and south of the dun. The dun is best viewed from the top of a large curious sheltered open area within a rocky outcrop that looks like it too could have been home to prehistoric people. A very interesting and truly ancient place to visit with care.