Humaitá Fortress, Military fortress in Ñeembucú Department, Paraguay.

Humaitá Fortress sits on a sharp bend of the Paraguay River and extends across several kilometers with earthworks and artillery positions. The site shows the remains of these defensive structures that once controlled river traffic.

Built from 1854 as Paraguay's main river defence, the fortress blocked the sharp horseshoe bend of the Paraguay River with a 1.8 km line of batteries and a chain boom. It held up the Triple Alliance forces for two and a half years before falling in the Siege of Humaitá in 1868, after which it was razed under the treaty.

The fortress's name comes from the Guaraní word for the sharp horseshoe bend in the river, and Paraguayans today regard Humaitá as a symbol of national pride and stubborn resistance. The site is remembered for the two-and-a-half-year delay it imposed on the Triple Alliance forces before it was taken in 1868.

The surviving earthworks run along the river bend, and the grassy embankment above the water is where the batteries once stood. Visitors walk the grounds on foot; the site is reached from the town of Humaitá in Ñeembucú Department. Allow time to follow the trench lines, which at their greatest extent stretched for 13 km.

The fortress used an innovative defense system with a chain boom stretched across the river and contact mines to stop enemy ships from passing. This obstacle forced attacking vessels to take detours or slow down, making them vulnerable to attack.