The island of Flat Holm (Ynys Echni) lies about 2¾ miles off the south Wales coast in the murky waters of the Bristol Channel, and is the southernmost point in Wales. It's managed by Cardiff Council as a nature reserve and SSSI, and has resident wardens all year round. It's famous for the transmission of the first ever wireless signals over the sea by Marconi in 1897. Boat trips run from Cardiff Bay in summer and unofficial landings are permitted, but all visitors have to pay a landing fee. Dogs are not allowed on the island. Facilities include toilets and a very small pub (The Gull and Leek) with outdoor seating. Buildings include a lighthouse, derelict isolation hospital and numerous WW2 lookouts and gun emplacements. Rabbits are abundant.
Coal Beach (above) and neighbouring East Beach are on the north-east corner, and are the arrival points for boats from the mainland. Both consist of steeply sloping shingle (mostly mudstone, limestone and some flint), and access is down good paths with steps. On the north-west corner lies West Beach. Also consisting of rocks and shingle, it's probably the island's best beach. On very low tides it's possible to walk around the island along the shore, and the two small coves of Point Bay and Dripping Cove become accessible.