Because of its proximity to San José, Parque Nacional Volcán Poás is one of the most visited National Parks in Costa Rica. It's an easy bus, taxi, or car ride through the countryside to the northwest of Costa Rica's major city. Additionally, the trails are paved with bricks or cement, which makes the route accessible even in the notoriously wet rainy season, which would otherwise be too muddy to consider. The crowds that visit the park don't quite allow for that wilderness experience most might seek, but it's a great introduction to a Central American cloud forest, with plenty of interesting flora and fauna, not to mention extraordinary geologic features, to whet the appetite.
Access to the main attraction, the steaming volcanic crater, is via a 600-meter paved trail called Sendero Sombrilla de Pobre (Poor Man's Umbrella Path – named after the giant tropical plant). Newly constructed viewing platforms allow a great vantage point regardless of how many other people are there. The fumeroles are still active, spewing steam through the crater's lake. The crater is often shrouded in mist and clouds (it is in a cloud forest, after all), but if it's out of view, try waiting a few minutes, as the wind can change conditions quickly.
After taking in the crater, continue the loop to Laguna Botos – a pristine volcanic lake. This crater is no longer active, and it has filled in with rain water. Due to the acidity of the soil, algae can't grow here, so the lake is crystal clear and reflects the sky and greenery beautifully.
The loop continues through the cloud forest, which is so dense that it provides some protection from light rain. Keep an eye out for all manner of epiphytes, including bromeliads and orchids. Seventy-nine species of birds have been identified here, including the resplendent quetzal, which is at the top of many bird-watchers bucket list, and several types of hummingbirds. Mammals aren't as abundant here, but you may notice tracks of coyotes, skunks, weasels, and the like.
After rejoining the Sendero Sombrilla de Pobre and taking it back to the headquarters, take a few minutes to explore the visitor center, which gives a fairly thorough history of the geology, fauna, and history of the area.
Entrance to the park is 1,000 colones for Costa Rican residents, or $15 USD for non-residents.