A short day trip from San Jose, Volcano Poas is a striking symbol of the powerful geothermal forces of nature that formed Costa Rica. Its main crater measures nearly a mile wide in diameter and is 900 feet deep, at the bottom of which lies a gaping hole filled with a bright green lagoon that spews boiling sulphurous gases. Water constantly seeps through cracks in the hot rock, evaporating and building pockets of steam. When the pressure in these pockets exceeds the weight of the water above, the steam breaks through in geysers that rocket up to 820 feet high. Poas is definitely an active volcano, but the last major eruption was in 1954.
Hiking trails surround Poas Volcano, most of which originate from the visitors’ center, each offering a different perspective of the volcano and the national park. The Escalonia Cloud Forest Trail is about half a mile long and is best for spotting the wide variety of birds that live there and the escalonia trees, which are notable for their distinctive pagoda shape.
A visit to the Poas Volcano is ideal in the early morning, when visibility is best and the weather is usually mild. As the day goes on, fog tends to accumulate, obstructing the view, and temperatures can drop to very chilly. The Poas Volcano National Park is open seven days a week from 8:00 am to 3:30 pm, and admission is $7 (half price for students with ID).