Otanaha Fortress, Portuguese colonial fort in Gorontalo City, Indonesia.

Otanaha Fortress sits on Dembe Hill with strong stone walls offering broad views across Limboto Lake and the surrounding Gorontalo region. The fortification consists of multiple interconnected structures strategically positioned on the elevated terrain.

The fortress was built in 1522 when King Ilato of the Gorontalo Kingdom worked with Portuguese sailors to construct this defensive structure. The construction used sand, calcium, and Maleo bird eggs as binding material.

The names of the three forts on Dembe Hill come from Naha's family: Otanaha combines ota (fort) with Naha, the son of King Ilato who found the structure in 1585; Otahiya is named for his wife Ohihiya, and Uwole means Pahu's fortress, after their son. Naha sheltered Ohihiya and their sons Paha and Limonu there during the war with Hemuto.

Reaching the fortress requires climbing 348 stairs divided into four sections with rest stops along the way. Visitors should plan time for breaks and be prepared for uneven surfaces.

An unusual detail of the construction was the use of Maleo bird eggs as binding material, combining local resources with Portuguese building techniques. This method shows how regional materials were integrated into European fortress engineering.