Situated at the confluence of two navigable rivers, Valdivia is one of the south's most charismatic cities. Nearby Spanish forts at Corral and Niebla are reminders of the city's importance during the colonial era, when it was one of few fortified cities maintained by the Spanish in Mapuche Indian territory; subtle German architecture dates from the late 19th-century influx of European immigrants. The Rio Cruces Nature Sanctuary, a protected wetlands north of the city, is home to a variety of aquatic birds and is a favorite destination for boat trips.