The settlement started in the 1800s as Riachão - a little riverside village that grew up around the old rubber trade. Mangabeira trees (Hancornia speciosa), native to the cerrado, produce a latex that Brazilian settlers harvested alongside the more famous Amazonian seringueiras. When muleteers crossing from Goiás to Bahia began stopping at Riachão, a chapel went up, the village took on a new name whose etymology is now lost - the origin of 'Mambaí' is unknown - and the settlement became a district of the municipality of Posse. In 1958 it was dismembered from Posse and became its own municipality. The rubber industry was already fading; cattle and subsistence agriculture filled in.

The Cachoeira do Funil is the municipality's best-known waterfall - and unusually, you can walk through a cave that sits beneath the falls themselves. A forest trail leads to the drop, and climbers can rappel from the top with a pendulum swing underneath the water. Above the fall, shallow pools make natural bathing spots with a water-massage effect from the current. The cave below requires a headlamp and some awkward climbing to enter, but from inside, the view of the cascading water - seen from behind rather than in front - is remarkable. Mambaí has dozens of these watery features, enough that local tourism has grown up around hiking trails and caving.

The Caverna Lapa do Penhasco is an energetic-moderate cave hike that tourists rate as essential - running water, a water crossing, abundant stones, and a dramatic interior chamber. Caverna Claraboia offers a stranger entry: it has a hole in the ceiling through which visitors can rappel into the cave from above. Cachoeira do Alemão - the German's Waterfall - sits at the bottom of a steep slope, rewarding the descent with clear, warm water good for long swims. And the Trilha Itaguassu links together a half-day loop through a cave cut by a river, with natural rock formations and swimming spots along the route. The guidebook shorthand is simple: Mambaí offers falls, caves, and underground rivers in denser concentration than almost anywhere else in Goiás.

For all the tourist appeal of the caves, Mambaí remains one of the poorest municipalities in Goiás. The population was 5,125 in 1980 and shrank through the 1990s before stabilizing. In 2006 the cattle herd numbered only 7,900 head - tiny compared to other Goiás municipalities - and the dairy herd was 480 cows, among the smallest in the state. Main crops are corn, sugarcane, beans, manioc, and rice, planted across modest hectares. Six schools serve the municipality. One hospital with 18 beds covers health. Adult literacy in 2000 was 75 percent, the lowest in Goiás. On the Human Development Index that year, Mambaí ranked 234 out of 242 state municipalities - third from the bottom.

Inside this small, remote municipality lives a small Romani community whose dialect attracted the attention of a University of Brasília linguist named Fábio José Dantas Melo. Professor Melo's study of the speech patterns of Mambaí's Romani residents became part of a broader project to document the Brazilian variants of Romani, a language that has traveled with its speakers across continents for centuries. The community itself is private about its daily life, but the academic record it has contributed to is real. In a corner of Brazil where the easternmost border of Goiás brushes up against Bahia and the limestone caves swallow rivers, the presence of a Romani community studied by academics and a tourist economy built on waterfalls gives Mambaí a depth of character out of proportion to its small population.