Gruta do Lago Azul
The entrance to Bonito's best-known show cave, a protected Natural Monument with a blue underground lake where divers found Ice Age mammal bones in 1992. Visits are guided walks; no public diving offer was found.
Visitors enter through a circular opening about 40 m across and walk down a steep chamber towards the lake on guided tours. The lake itself is not open to visitors in any source reviewed: the 2012 state order covered contemplative visits only.
The site matters to cave diving for what divers found there. In 1992 Brazilian and French divers recorded bones of extinct Pleistocene mammals on the lake floor, and the lake hosts cave-adapted aquatic life, including the blind crustacean Potiicoara brasiliensis.
The environment
A large, steeply sloping dry chamber ending in a still, clear underground lake. A 2002 report gave the lake as 90 m deep. Sunlight strikes the water in part of the year, turning it an intense blue.
Conditions
Light effect on the lake is strongest from about September to February according to a 2021 report; other sources give different months and morning hours.
Typical ranges from published sources, not current conditions.
Facilities
Guided walking route into the cave. Showcaves.com lists tours of about 90 minutes and no entry for children aged 0 to 4 (data from 2000 to 2020).
Every fact on this page, with its source (9)
| Fact | Status | Source |
|---|---|---|
| The entrance is circular and about 40 m across. | Reported | [3] |
| The underground lake is 90 m deep.Single 2002 figure; no survey found. | May be out of date | [4] |
| In 1992 Brazilian and French divers found Pleistocene mammal bones on the lake floor. | Reported | [4] [5] |
| The 2012 IMASUL order authorised contemplative visits only, capped at 305 visitors a day in groups of up to 15 with a guide, and does not mention diving.Authorisation ran to 2013-12-31; later visitor rules are in the 2022 management plan, which could not be read for this record. | May be out of date | [1] |
| IMASUL approved the monument's management plan on 12 July 2022. | Verified | [2] |
| The federal government authorised ceding the cave to Bonito municipality for 20 years in January 2021, with the municipality managing visits. | Reported | [3] |
| Visits required a registered local guide, a voucher único, a helmet and closed rubber-soled shoes under the 2012 order.2012 rules. | May be out of date | [1] |
| From September to February sunlight on the lake turns the water an intense blue.Showcaves gives about 07:30-09:30 each morning; FAPESP (2002) gives December and January. | Reported | [3] |
| Showcaves lists guided tours of about 90 minutes and no entry for children aged 0 to 4.Reference data dated 2000-2020. | May be out of date | [5] |
Verified: stated by an official or primary source we opened. Reported: from a secondary source only. Sources conflict: the note gives both versions. May be out of date: the newest source we found is old.
Written in our own words from the sources above. Report a correction