Fort Reina Luisa sits above the Rahue River on the edge of the city, the most intact remnant of colonial Osorno. The original fort dates from 1793, built to protect the refounded city against Mapuche raids from the interior. The current structure, restored in the 20th century, houses a small regional history museum covering the city's colonial period, its destruction in the 18th century, and the subsequent German immigration that shaped its present character.
The museum is small but useful for understanding why Osorno looks the way it does — the German influence on the architecture, the dairy and cattle economy, and the landscape of the Los Lagos region. The fort's position above the river offers the best view of the Rahue valley and, on clear days, the cone of the Osorno volcano to the northeast.