About 4km north of Archidona, you’ll find Cuevas de Jumandí. This cave system, the best known in the area, has three main branches that remain partly unexplored. Forgo the sketchy waterslides that dump into a river-water pool, and tread slowly (with a flashlight) to see stalactites, stalagmites and odd formations. Rubber boots and old clothes will serve you well.
For thorough exploration, you’ll need a guide from Tena or on-site – ask guide companies in Tena for a customized day trip to the caves.