Brean Down is a promontory marking the eastern end of the bay. Made of carboniferous limestone, it is a continuation of the Mendip Hills, and two further continuations are the small islands of Steep Holm and Flat Holm. It is owned by the National Trust, and is rich in wildlife, history and archaeology, as well as being a Site of Special Scientific Interest in its own right. It is bounded by steep cliffs and, at its seaward point, Brean Down Fort built in 1865 and then re-armed in the Second World War. There is evidence of an Iron Age hill fort, prehistoric barrows, field systems and a pagan shrine. The shrine dating from pre-Roman times was re-established as a Romano-Celtic style temple in the mid-4th century and probably succeeded by a small late-4th century Christian oratory. In 1897, following wireless transmissions from Lavernock Point in Wales to Flat Holm, Guglielmo Marconi moved his equipment to Brean Down and set a new distance record for wireless transmission.