The town's defining sight and a UNESCO World Heritage Site. The castle was built by the Swedes in 1653, taken by the Danes, then captured by the British in 1664, who held it as the headquarters of the Gold Coast colony until 1877. For most of those two centuries it was a slave-trading depot. Up to 1,500 enslaved Africans at a time were held in the male and female dungeons below the courtyard before being shipped out through the Door of No Return.
The standard guided tour, run by knowledgeable Ghanaian guides, takes about 90 minutes and goes through the dungeons, the punishment cells, the governor's quarters, and the small but exceptional museum on the upper floor (the West African Historical Museum, with rotating exhibits on the Trans-Atlantic slave trade and the cultures it shattered). It is a devastating, essential, and very hot visit — bring water. The museum is one of the best in West Africa.