La Fortuna sells more tours than anywhere else in Costa Rica, and most of them are variations on four things: the hanging bridges, the volcano trails, the hot springs, and a river. Almost every hotel will book them, at a mark-up.
Rafting here is the easy introduction — half a day on the Balsa, class II and III — while the serious water is a long day away on the Sarapiquí or the Pacuare. The volcano itself has been quiet since 2010, so what you are paying for is the forest around it rather than lava.