The Blue Lake Cave (Gruta do Lago Azul) near Bonito, in Mato Grosso do Sul, Brazil, is a limestone cavern world-famous for the deep-blue subterranean lake that sits more than 40 metres below its circular entrance. When sunlight reaches the water it glows an intense cobalt blue, and the lake is over 80 metres deep with a bottom that has never been fully mapped. Designated a Natural Monument in 1978 by Brazil's institute for historic and artistic heritage (IPHAN), it is also a major scientific site where Ice Age megafauna fossils (giant sloth, sabre-toothed tiger) and prehistoric human remains have been recovered from the water. As of 2026 it remains a strictly capacity-limited, conservation-first attraction: a contemplative tour with no swimming and no contact with the formations.
The intense cobalt-blue subterranean lake, most vivid when morning sunlight strikes the water
Natural light pouring through the circular mouth into the vast limestone hall
Intricate speleothems — stalactites and stalagmites shaped over thousands of years
Geological and paleontological importance: fossils of Ice Age giant sloth, sabre-toothed tiger and armadillo found here
The sense of scale as the underground chamber unfolds during the steep stairway descent
Good to know
RulesAll of Bonito uses a mandatory single-voucher system: you must pre-book a date and time slot through an accredited local agency. Prices are fixed and there is a daily visitor cap, so slots sell out fast in high season (confirm current price and hours).
SafetyReaching the cave means descending — and climbing back up — a steep stairway of over 100 metres; a reasonable fitness level is needed. The wet rock is slippery, and closed-toe shoes are mandatory.
SeasonThe water is bluest from September to February, and most striking under morning light. However, heavy rain during the wet season (roughly November–March) can cloud the water or suspend visits, so an early-morning slot is best.
MannersThis is a strictly contemplative tour for preservation: no swimming, no touching the water, no touching the formations. Move quietly in small groups of about 15 with your guide, and do not touch any structures.
CautionBecause prices are officially fixed, avoid street or unlicensed sellers touting 'special discounts' and book only through accredited agencies. Watch for inflated transfer prices between Campo Grande and Bonito, and carry cash since the area is remote.
SafetyThe cave is about 20 km from town at the end of an unpaved road, so allow extra travel time. Missing your booked slot can mean cancellation with no refund; leave early and bring water and sun protection.
Practical info
The cave lies about 20 km southwest of Bonito town and can only be entered with a voucher pre-booked through an accredited agency. The nearest major airport is Campo Grande (CGR, ~300 km, 3–3.5 h by shuttle or rental car); Bonito also has a small airport (BYO) with limited flights. It generally opens from around 7 a.m. to early afternoon (about 2–3 p.m.) and the tour lasts roughly 1 hour 20 minutes (verify current hours and prices before visiting).
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