Marine Peilstand 1 tower, or MP1 tower, was used to observe targets at sea. The round tower is around 16 metres (52 ft) tall, and has four observation floors, each with a wide, and narrow embrasure (for observation purposes only). Each of these floors was assigned to observe for one of the four 15 cm naval guns. The tower has five floors, including a windowless lower floor, plus a further open rooftop floor.