The cave runs to somewhere between 1,100 and 1,200 metres of passage, arranged as a sequence of nine halls, and reaches roughly 75 metres below the level of its entrance. An underground river moves through it. Visitors see a fraction of that: about 450 metres of gallery, lit, with a vertical descent of some 35 metres over the course of the walk. The halls are named after what people decided their formations resembled, which is the universal convention in show caves and never gets less endearing. Bats live here, as they do in every warm limestone cavity in the tropics, and their presence is part of why the deeper sections stay closed.

The famous approach is the cable car. It runs about 550 metres from the plateau rim down the face of the escarpment to the cave mouth, and the trip takes three minutes — long enough to register that the forest canopy below is a very long way below, short enough that there is no time to reconsider. It is operated by the state tourism department and has spent stretches out of service, at one point for two years running, which is worth checking before committing to a plan built around it. The alternative is to walk. The Trilha dos Cafundós descends the same escarpment on foot, with a credentialed guide, twelve kilometres round trip and about seven hours door to door, including roughly 500 metres inside the cave. Departures go at nine and ten in the morning. Nobody who has done both describes them as equivalent experiences.

The cave has been known since the early eighteenth century, when Portuguese colonists came through the region prospecting for minerals — silver above all. They found very little. A persistent local explanation holds that part of the cave is not natural at all, but the residue of those excavations, widened by two centuries of weather since. The geology argues otherwise, but the story is durable, and it says something about how much effort was thrown at this escarpment for so little return. Other caves honeycomb the same limestone and stay closed to visitors: the Gruta do Urso Fóssil, which is paleontologically important; the Gruta do Morcego Branco, the white bat's cave; the Gruta de Cima; and the Gruta do Pendurado.

Ubajara National Park was created on 30 April 1959 by federal decree 45,954, covering 4,000 hectares. In April 1973 it was cut down to 563 hectares — a reduction of more than eighty-five percent — and it stayed that way for nearly thirty years before a December 2002 expansion restored it to roughly 6,288 hectares. Even now it is the smallest national park in Brazil. It occupies land in the municipalities of Ubajara, Tianguá and Frecheirinha, sits between about 720 and 840 metres above sea level, and is administered by ICMBio. Immediately around it lies the Serra da Ibiapaba Environmental Protection Area, an altogether different order of thing at more than 1.59 million hectares.

The escarpment does something useful to weather. Moist air rising against the Ibiapaba wall drops around 1,440 millimetres of rain a year on the high ground, and the result is that a single short slope carries humid forest at the top, transitional forest in the middle, and caatinga — the semi-arid thorn scrub of the northeast — at the bottom. Temperatures run between 16 and 28 degrees, averaging around 22, which by the standards of interior Ceará is remarkably mild. Surveys have counted 41 mammal species, 127 birds, 16 lizards, 17 snakes and 16 amphibians in that compressed space. Among them are the oncilla and the cougar, the red-handed howler monkeys of Maranhão, and two small frogs, *Adelophryne baturitensis* and *Adelophryne maranguapensis*, that exist in only a handful of Ceará's forest fragments.