This reserve is 102 km² in size and is located in the province of Alajuela. Caño Negro is a wetland area near the border with Nicaragua. During the rainy season (May to October), the banks of the Río Frío overflow, creating an 800 hectare lake. In the following months, the water level drops again and large numbers of migratory birds from North and South America hibernate in Caño Negro. Caño Negro is one of the most important wetlands in the world. It has been a protected nature reserve since 1984. You can see the richness of the nature reserve by boat. Well over 400 resident and migratory bird species having been recorded here, including many not easily seen elsewhere in Costa Rica.
Most visits start out at Los Chiles where you board a boat and glide up the Río Frío through canyons of green towards the everglade like Lago Caño Negro. Another option is via Ruta 138/Upala-Caño Negro Los Chiles. There enter a boat at Caiman Bridge over Rio Frio.