A biological reserve on the margins of the Tarcoles River just SE of Orotina in Puntarenas Province, this was founded in 1978 and has an area of 4,700 hectares.

Located in a transition zone between the dry forest and humid forest of the Costa Rican North Pacific region, this reserve protects ecosystems not found in any other conservation area. It also is an island of forest completely surrounded by land dedicated to human activities.

The reserve has a number of marshes which are part of the area seasonally flooded by the Tarcoles River. Although there are disturbed and secodary forests, primary forest makes up the majority of the reserve.