Castillo San Miguel de Agüi, Spanish colonial fortress in Ancud, Chile

The Castillo San Miguel de Agüi is a Spanish colonial fortress on the Lacuy Peninsula that overlooks the Chacao Channel from an elevated position. The site features stone walls and cannon batteries arranged to defend against approaching vessels.

The fortress was built in 1779 as a strategic outpost to guard against piracy and foreign attack along the Chilean coast. It maintained defensive importance until the early 1800s, when its military role gradually diminished.

The fortress displays the military architecture that Spain built along this coast during colonial times, using local stone and defensive layouts. Visitors can observe how Spanish forces organized their coastal settlements and protected their territorial interests.

The fort lies on the Lacuy peninsula, about 26 km from Ancud, reached by vehicle over rural roads. The 1960 Valdivia earthquake brought down the fortified gate and the underground cells, so the ruins are uneven ground. Part of the site was remodeled in 2012 with Inter-American Development Bank and SUBDERE funding.

The 1960 Valdivia earthquake destroyed the fort's underground cells and brought down the fortified gate, so no original entrance survives. The cannons seen at the site today are part of the artillery renewed while the Chilean Navy still operated the fort in the early 20th century.