The Arenal volcano, an almost perfect 1,670-metre cone, erupted continuously from 1968 until 2010, when it entered a resting phase. For four decades you could watch glowing lava at night; you cannot now, and it is worth knowing before you travel, because many circulating photographs date from that period.
The national park
Arenal Volcano National Park has trails crossing lava flows from 1992, now colonised by pioneer vegetation, up to viewpoints facing the slope. The Tucanes trail and the main lookout combine into two or three hours. The volcano is usually clear first thing in the morning and clouds over afterwards: if you want to see it, get up early.
Cerro Chato, the adjacent cone with a crater lake, has been closed for years due to erosion and risk, though some private routes offer alternative access.
Hot springs
Volcanic heat feeds thermal rivers, and an entire industry has grown around the volcano. The large resorts offer dozens of stepped pools among gardens, at varying prices and levels of crowding. The free alternative is the Chollín river, a stretch of hot water under a bridge where locals bathe: no facilities, keep an eye on your belongings, and a considerably more genuine experience.
La Fortuna waterfall
The La Fortuna waterfall drops some seventy metres into a rainforest amphitheatre. You descend about five hundred steps and must climb back up, which in heat and humidity is harder than it sounds. Swimming in the lower pool is possible, though the current near the fall is strong.
The lake and around
Lake Arenal, an artificial reservoir supplying a large share of the country's electricity, stretches west of the volcano and offers excellent windsurfing thanks to steady winds from December to April. Nearby are hanging bridges, zip lines, the trail to the Poza Azul, and coffee and cacao plantation visits.
Base and climate
La Fortuna is the base town, with all the accommodation and restaurants. It rains far more here than on the Pacific: expect showers even in the dry season, and do not plan an entire day outdoors without a fallback.
A note on the 1968 eruption
Arenal was thought to be extinct until 29 July 1968, when it erupted without warning and destroyed the villages of Tabacon and Pueblo Nuevo, killing around eighty-seven people. The town of La Fortuna was spared because the blast went the other way, which is where its name — the fortunate one — is often said to come from. The lava fields you walk across on the park trails date from that four-decade active phase.