Castletown (Manx Balley Cashal), a seaport and former capital of the Isle of Man, on Castletown Bay, 11 miles SW. of Douglas by rail. Castle Rushen, now a prison, occupies the site of a Danish fortress of the 10th century, which was almost wholly demolished by Robert Bruce in 1313. The grounds of Rushen Abbey (11th century), near the station, are now market-gardens.
Hard by is the small building where the House of Keys assembled for about 170 years. Brewing, tanning, and lime-burning are carried on. Near Castletown is King William's College (1833), an Elizabethan pile, rebuilt after the fire of 1844, and enlarged in 1862. Pop. (1851) 2479; (1891) 2178.