The Otanaha castle was the fort of the Kings of Gorontalo. They used a special mixture of building materials in the construction including sand, mortar and the egg white of the hammer -headed hen. The castle is lying ona hilltop at the border of the Dembo village, therefor it has a beautiful view of the Limboto Lake. The castle is located at 8 km from the city center of Gorontalo. There are also two other castles in the area: Otahiya and Ulupahu. To visit the three castles the visitors need to take 345 steps, but there is an alternative route to the castles as well.