This is the National Museum of Costa Rica. The fortress was built in 1917 and was originally a military barracks: the exterior walls still have many bullets lodged in them from the country’s 1948 civil war. It became the site of the museum in 1950.
The entrance on the east side leads to a courtyard displaying pre-Columbian artifacts and cannons from the colonial period. The museum is organized thematically in a counter clockwise direction from the entrance with artifacts related to Costa Rica’s geological, colonial, archaeological, religious and modern history.