Abismo Anhumas, Bonito MS: abseiling 72 metres into a lake underground

The Abismo Anhumas is the strangest thing you can do in Bonito: the entrance is a crack in the ground and the only way to the lake below is to abseil down. It requires training the day before, has a small daily quota and resembles nothing else in the region.

What the Abismo Anhumas is

The Abismo Anhumas is a vertical cave on a farm in the Bonito region. The opening in the ground is discreet and prepares nobody for what lies beneath: an enormous chamber full of limestone formations, with a clear lake at the bottom. There are no stairs, no ramp and no alternative route — anyone who wants to see it up close abseils down a rope, roughly 72 metres of controlled free descent.

That makes it one of the few attractions around Bonito where the access itself is the central experience. The descent takes several minutes and crosses three distinct environments: the open air at the mouth, the half-light of the middle section and the lit darkness of the chamber, where any sense of scale disappears.

The training the day before is not optional

This is the fact that wrecks the most badly planned itineraries in Bonito: to descend into the Anhumas you must complete abseil training, held on a separate occasion — normally the day before, on a tower at the operator base. There you learn to work the descender, practise your posture and are assessed.

That means the Anhumas occupies two slots in your diary, not one, and that you cannot decide in the morning to do it that afternoon. Anyone arriving in Bonito with two days who wants to include the abyss has to build the itinerary around it, not the other way round.

Contemplation, snorkelling and diving

Once at the bottom, what you do on the lake depends on the option booked. The contemplative version crosses the chamber on a floating platform without entering the water. The snorkel version adds mask and snorkel to see the submerged formations from above. Scuba diving, restricted to certified divers, goes down among the cones.

The way back up, in all of them, is by a mechanical hoist operated by the guides — you do not climb.

Who it suits, and who it does not

• It suits anyone who wants something that repeats nowhere else in the itinerary.
• It suits anyone with two days in town willing to give one of them to the abyss.
• It does not suit anyone whose fear of heights would freeze them: the descent is long and there is no halfway.
• It does not suit anyone with heart, spine or mobility conditions without medical clearance.
• It does not suit large groups with rigid schedules: the daily quota is small and sells out early.

When to go

Being underground, the Anhumas is little affected by rain on the day. What rain does affect is access to the farm and, in extreme cases, visibility in the lake. Season matters more for availability: because the daily quota is low, high season sells out weeks ahead.

Frequently asked questions

Do I need previous abseiling experience?

No. The training exists precisely for people who have never done it. What you cannot do is skip the training.

Do I have to climb the rope back up?

No. The ascent is done by a mechanical hoist operated by the team, with you seated in the harness.

Can someone claustrophobic manage it?

The chamber is vast and does not feel tight, but descending through a crack with no quick way out bothers people with that condition. It is worth talking to the operator beforehand, frankly.

Written by: Adriano Habermann Last updated: September 13, 2026