The entrance to Old Town Tallinn is through the archway entry gate which is guarded by the round and squat Fat Margaret Tower. Fat Margaret was built between 1511 to 1530 during the reconstruction of the medieval city gate system. It is 82 feet in diameter and 65 feet high. The walls are up to 16 feet thick. The origin of the tower’s name is unknown. In addition to being a fortification against would-be invaders during medieval time, Fat Margaret had been used as a storehouse for gunpowder and weapons and as a prison. Today the Estonian Maritime Museum is located in the Fat Margaret tower. On the other side of the old town, next to the Estonian Parliament building, is the round Tall Hermann Tower. The first part was built 1360-70. It was rebuilt in the 16th century. A staircase with 215 steps leads to the top of the tower. The tower consists of ten internal floors and a viewing platform at the top.