Porth Castell and Porth Diana are two neighbouring small sandy coves, just a short walk south of Trearddur Bay on Anglesey's Holy Island. Both are backed by a sea wall and flanked by rocks of mica-schist.
Porth Diana (above) is the larger of the two, and much used by the local yacht club for moorings. Porth Castell is just to the south, and is a better choice for swimming.
Ravenspoint Road runs behind the beaches and roadside parking is possible further along the lane, but suitable places are readily taken. Alternative parking is at Trearddur Bay. Dogs are allowed at all times.
Anlglesey's county flower - the spotted rock-rose - can be seen at the Porth Diana nature reserve, reached along a public footpath from Ravenspoint Road behind Porth Diana.