Situated on the South West corner of Inishowen is Inch Island, attached to the mainland by a wide causeway. Between Inch Island and the mainland lies a region of drained polder land, which has an area of 1,200 hectares. Here Whooper Swans are of international importance with on average 6,000 birds over-wintering. During the 15th century, Sir Cahir O’Doherty built a castle near the southern end of the island, parts of which are still visible today. There is also a fully functioning pier on the northern side of the island with easy access to Lough Swilly.