Beneath La Fortuna the lava is still curdling and heating countless bubbling springs. There are free, natural hot springs in the area that any local can point you toward (ask about 'El Chollín'). If you’re after a more comfortable experience, consider one of the area’s resorts.
Although it’s not currently active, Volcán Arenal is the big draw here. There is a well-marked trail system within the park, and several private reserves on its outskirts. Waterfalls, lava flows and crater lakes are all worthy destinations that you can reach without a guide.
In November 2017, four Dutch tourists were injured, a couple rather severely, when they were caught in a landslide in the off-limits area (within 4km of the crater) of Volcán Arenal. It took more than a day to rescue them and their Costa Rican guide from the mountain. So, quite literally – don't go there.
Kayaking, Canoeing & Rafting
La Fortuna is not a river-running hub like you’ll find in other parts of the country, but there are a few companies offering canoeing and kayaking in the area. If you wish to go white-water rafting, tour companies do take groups from La Fortuna to run the Sarapiquí and other distant rivers. Some offer the option to get dropped afterwards in San José or on the Caribbean coast – a good way to have some fun on a travel day.