The Carlos Anwandter Nature Sanctuary (Santuario de la Naturaleza Carlos Anwandter) protects the wetlands of the Cruces River system north of Valdivia, an internationally important Ramsar-listed wetland that is the only protected wetland in Chile's Los Ríos Region. The sanctuary is known primarily for its birdlife — the reed beds and shallow lagoons attract over 100 species including black-necked swans (Cygnus melancoryphus) in large numbers, many species of ducks and herons, and the coipo (Myocastor coypus), a large semi-aquatic rodent that is common but rarely seen elsewhere in this density.
Boat tours from Valdivia navigate through the wetland channels, providing close views of the black-necked swans that winter here in particularly large numbers. The same boats are used for the longer river journeys to the Niebla forts, but shorter wetland-specific tours are also available. The sanctuary is also reachable on foot along the Cruces River bank from the northern edge of Valdivia; the walk gives access to several observation points for birds. Dawn and dusk are the best times for bird activity.