Castletown, Isle of Man House of Keys moved from Castletown to Douglas. The Isle of Man Census 2011 lists the town's population as 3,097 (2006: 3,109) It is the fourth largest town on the island, after Douglas, Ramsey and Peel, but is also smaller than Onchan and Port Erin, which have the status of villages. The town lies on the northwest side of Castletown Bay. The opposite shore of the bay is the west coast of the distinctively-shaped Langness Peninsula. To the north-east are Ronaldsway Airport and industrial zone, and the village of Ballasalla; to the north-west the villages of Ballabeg and Colby; and
Castletown, Isle of Man to the west Port St Mary and Port Erin. The older parts of the town are largely built of local grey limestone. At Scarlett, a short distance to the south of the town, there are the remains of an ancient volcano and various other features such as fossils and thick sheets of limestone. The A3 road connects Castletown with Ramsey via St John's, while the A5 road (also known as New Castletown Road as opposed to the Old Castletown Road which takes a more rural route nearer the coast) connects the town with Douglas to the north-east and Port Erin