It is formed by a block of Eocene basalts, 60-60 million years old that rose up due to subduction of the collapse of the Cocos Plate under the Caribbean Plate along the Central American Trench. The maximum altitude is 110 m and most of the coast consists of cliffs up to 70 m high in the process of eroding. The beaches are small, not over 100 m long, their white sands sometimes almost disappear at high tide.
The island has great archaeological significance as it was used as a cemetery and a permanent Pre-Columbian settlement. It is still possible to observe the remains of pottery and some almost perfectly round stone spheres made by the Indians that have given rise to several hypotheses regarding their origin and utilization.
The central 90 high plateau is covered in a very tall evergreen forest, basically consisting of enormous cow tress (Brosimum utile), also known as milk tree because of the white latex it exudes and which can be drunk. It is thought that these gigantic trees come from an orchard planted by the natives. 158 species of plants have so far been recorded on the island.
Although animals are scarce, several birds such as the osprey (Pandion haliaetus) and the brown booby (Sula leucogaster) can be observed. Entomologists have recorded 5 species of beetles, 4 of butterflies, 2 of moths, and 7 of bees. Among the mammal: the grey four-eyed opossum (Philander opossum) and several species of rats and mice have been seen. Among the amphibians and reptiles, records include the transparent tree frog (Centrolenella fleishmanni) and the boa (Boa constrictor).
Around the island there are five platforms or low coral reefs amongst which 15 species of scleractinia corals can be distinguished and where Porites lobata stands out for sheer numbers. Two species found in the waters around the island are the lobsters (Panulirus sp.) and the giant conch (Strombus galeatus).
The Isla del Caño is 16.5 km west of the Osa Peninsula. Prior permission from the ACOSA authorities is needed in order to visit it. Access is by sea using boats suitable for crossing open sea that can be contracted at the landing in Sierpe, 15 km from Palmar Norte, and in Golfito.
Camping is not allowed, but daily visits can be made. Diving, which is for extraordinary experience, is only allowed in areas designated under the Public Use Regulations of this reserve. There is a path across the island as far as the archaeological site, and a picnic area with tables, toilets and drinking water. There as a bus service between San José and Golfito with a station in Palmar Norte. In Palmar Norte one can find boarding houses, restaurants and grocery stores, and taxis can be hired. In Sierpe there is a hotel.