This historic site includes several structures. The most impressive is Fort Christiansvaern (1749), a four-point citadel occupying the deep-yellow buildings on the town’s east side. Built out of Danish bricks (brought over as ships’ ballast), the fort guarded against pirate onslaughts, hurricanes and slave revolts. Cannon on the ramparts, an echoey, claustrophobic dungeon, and latrines with top-notch sea views await inside. The fort entrance has brochures for self-guided exploration of the other nearby historic buildings.