Barra means bar or river mouth, and the name is literal: this is the place where the Garças joins the Araguaia, one of the great rivers of central Brazil. The Araguaia here is wide, shallow and sandy, and in the dry season it retreats to expose freshwater beaches that draw Brazilian families the way an ocean coast would. The town was founded on 13 June 1924 and became a municipality of its own on 15 September 1948. It now ranks among the largest cities in Mato Grosso, sitting at the midpoint of the BR-070, the highway that runs from Cuiabá to Brasília — roughly 470 road kilometres to the state capital in one direction, 530 to the federal capital in the other. That central position on the map is more than a boast: the Serra Azul escarpment just outside town holds the marker for the geodetic centre of Brazil.

The Serra do Roncador is a long escarpment of cerrado-covered sandstone, and it dominates the country north and east of town. Part of it is protected as Serra Azul State Park, 11,002 hectares of savanna, waterfalls and cliff edges that have become a favourite launch site for paragliders — the thermals off the rock face in the dry season are reliable enough to hold a wing up for hours. Hot springs bubble out of the ground nearby, and water parks have grown up around them. On a clear morning from the top of the escarpment you can see the two rivers converge and the town spread out in the fork between them.

In the 1990s the municipality poured concrete for a discoporto — a spaceport for flying saucers. Nothing has ever landed on it. That has not slowed the phenomenon it was built to serve: Barra do Garças has become one of Brazil's centres of ufological tourism, drawing people who believe the Roncador is a place of unusual activity. Residents report strange lights over the escarpment. Visitors arrive convinced that the range hides crystal skulls, or a subterranean city, or a portal that opens onto Machu Picchu and links this place to the origins of the Inca. None of that is established fact, and the town does not particularly need it to be. What is documented is the belief itself, and the steady stream of seekers it brings up the BR-070 — a Brazilian Roswell, complete with its own souvenirs, its own local celebrities, and its own patient concrete circle waiting for a guest.

Some of the mystique predates the flying saucers by decades. In 1925 the British explorer Percy Fawcett went into the Mato Grosso backlands looking for a ruined city he called Z, taking his eldest son and his son's friend with him. They were never seen again, and the Serra do Roncador is among the regions long associated with their disappearance. What actually happened to the three men has never been established — a century of expeditions, rumours and rival theories has produced no body and no ruin. The unresolved ending is exactly the kind of thing a landscape like this holds onto. Fawcett's lost city and the Roncador's lights are separate stories, but they feed the same appetite: the sense that this country has not finished being explained.

Strip away the mystery and Barra do Garças is a busy regional hub. Cattle and grain move through it. The BR-070 keeps trucks rolling past at all hours. A small airport handles light aircraft, with most traffic arriving from Cuiabá. Kids swim off the sandbars in the dry months. The city is close enough to Goiânia, Brasília and Campo Grande to serve as a natural stop on a long crossing of the interior, and far enough from all of them to feel like the frontier it recently was. The Christ statue looks out over both — the rivers and the ordinary town — from a hill that, on some nights, people insist is not the only thing watching.