The North Gate
Visit to the tourist attraction of Sweden - the part of Visby city wall - The North Gate: is one of the oldest towers in the city wall and was the main entrance to the town for people and goods from the north part of Gotland.
Wikipedia: Originally, there was only a simple gate in the wall. The original slot for the toll barrier, dressed with wood, is still visible. The tower was built shortly after the erection of the first wall, possibly as early as 1280. The tower lies on a steep slope. It was stoutly built, and hence had good defensive capacity. The outer, wooden gates were reinforced with a portcullis. Openings for chains and ropes to pull it up still exist. Through other openings, water could be poured onto the portcullis if an enemy attempted to set it on fire. During times of peace, the gates were normally open and the entrance only blocked by the chain. The rooms above the gate contained a fireplace, which proves that the gate could have been permanently manned throughout the winter. On several of the floors, the arrow-slits have been widened to accommodate cannons. At the top of the tower, there are traces of an external wooden gallery for archers.