If you are up for a little more strenuous hike with a huge pay-off, Rio Celeste on the side of Volcan Tenorio is one of the best in Costa Rica. Take the Inter-American south of Liberia and turn left on Route 6 before you reach Canas. A rough but paved road leads up past Upala, and here there are a selection of resorts to choose from [more on this later]. Many choose to spend the night here so that the proper time can be given to prepare, enjoy and unwind from the hike. We recommend a guide, available at any hotel, and sturdy shoes. Beyond Upala, your guide will lead you to a rough dirt road that leads up the side of Volcan Tenorio and into the cloud forest. We saw a sloth on the way that the guide seemed to know would be there, high in a tree. I guess that speaks to how slowly they move. The rough, seemingly endless road ends at a Visitor's Center with a restaurant in an extremely remote setting. From there, the 3-hour loop hike can easily stretch to 4 hours as you discover the Blue Lagoon [see photos]. We saw a green basilisk dance across the azure water from one side to the other. If your guide is knowledgeable, he/she will show you where the Rio turns from clear to blue as it crosses a vein of copper sulfate. There are bubbling hot pools in the river that we soaked in [although I have since heard this is no longer allowed]. And then, at the mid-way point of the hike, is the big pay-off. This amazing waterfall plunges into a blue lagoon that you can wade in. In fact, you'll need to take you boots off to cross the river and follow the trail.
So many more experiences await you on this trail, but I will save that discovery for those who find it.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.