Lojsta Castle, Medieval fortress ruins near Stånga, Sweden

Lojsta Castle is a medieval fortress ruin on an island between two lakes in Gotland, Sweden. The stone foundations and the remains of its defensive moat are still visible today, showing how the stronghold was structured.

This fortress was built during the Middle Ages and later served as a base for pirate groups. In 1404, the Teutonic Knights seized control and eliminated the pirate presence.

The name Lojsta is shared with the parish and the nearby lakes. The fortress is identified with Gullborg, a stronghold written about in 1390s sources. Visitors can still make out the moat and embankment that separated the inner courtyard from the outer bailey.

The ruins now stand on dry land between the Slottsträsk and Broträsk lakes, reachable on foot; the medieval drawbridge to the mainland is gone, though traces of it remain. The site is wooded and the turf-covered house foundations and earthworks lie under trees, so sturdy footwear helps. Lojsta Hall, a reconstructed Iron Age building, stands about 150 m northeast by the parking area.

Early archaeological digs in the 1900s uncovered the fortress's layout and defensive features. These excavations helped researchers understand how medieval Swedish fortifications were designed and built.