Parque Cuevas Volcánicas
Halfway up Volcán Villarrica, you find this cave right next to a very basic visitor center. It first opened up in 1968 for spelunkers to explore, but eventually tourism proved more lucrative. A short tour takes you deep into the electrically illuminated cave via wooden walkways that bring you close to the crystallized basalt formations. Your tour guide may make occasional hokey references to witches and pumas hiding in the rocks, but it's definitely worth a visit—especially if uncooperative weather prevents you from partaking of the region's other attractions and activities.
