Last Updated: Oct 18, 2013
Staring into the main crater on a clear day visitors can see the plumes of sulfuric gas and water vapor rising from the Poas Volcano. Inside the crater's center bubbles the world's largest, most acidic lagoon. The main crater is the second widest in the world, nearly a mile in length, and more than 900 feet deep with a layer of liquid sulfur at the bottom.
Location: : Poas Volcano National Park; 23 miles north of Alajuela
Altitude : 8,900 feet above sea level
Highest Visibility : May - November
Hours : 8 a.m. to 3:30 p.m. daily
Telephone : 506-2482-2165
Entrance Fee : $10
An hour outside San Jose, the drive to the volcano is paved. At the entrance is a cafeteria, museum and gift shop where raincoats are purchased on unexpected rainy days. The trail to the main crater is wheel-chair accessible.
North of the active crater is the long-extinct Von Frantzius composite cone, the oldest crater in the central volcanic mountain range. Today it's known as Botos lagoon. A stark contrast to the main crater, the lagoon is cool, blue and surrounded by the dense vegetation of the area's cloud forest. From the lake, a stream runs down the volcanic slopes into the Sarapiqui River.
In 1910, Poas Volcano erupted, blowing ash 26,000 feet into the air and creating the largest geyser the world had ever seen. The 1952-1954 eruptions cause more ash clouds, thick with fire and rocks. The volcano has since settled in activity, though smaller gas emissions have increased creating acid rain that damages strawberry and coffee crops west of the volcano.
The best time to visit the volcano is from May to November - the earlier in the day the better. Walking the main trail will take visitors to the main crater. From there, visitor can take two different trails, one leading to the Botos Lagoon, the other leading back to the main building.