Found 37 Km North of the city of Alajuela, this 5,600 hectare park was formed in 1971. It centers on Poas Volcano, one of the most spectacular in the country. This volcano is considered to be the active volcano with largest crater in the world.

Its eruptive history includes an eruption in 1910 that blew clouds of hot ash over 8,000 meters into the sky. In its last eruptive period (1952-1954)it threw off clouds of ash and incandescent rocks. between these perioods it is not necessarily quescent, often coughing out some ash or steam.

About 60% of this park is covered with primary forest. This is mixed with patches of regenerating secondary forest, slowly replacing forest destroyed by eruptions or, in some cases, damage by man. Some areas near the crater are covered by that weirdly beautiful dwarfed forest seen in these situations, elfin forest.

Among the mammals seen there are the wild goat, 2 species of monkeys, the armadillo, tepescuinte (giant jungle rodent), the tapir and several felines. The crater often attracts large flies due to sulfurous gases similar to some given off by the decomposition of rotting flesh.