A giant, sponge-like dome in central Brazil towers over the surrounding landscape, and it acts as a natural water collector that feeds the region’s famous hot springs. The Caldas Novas dome, also known as Serra de Caldas, is a 12-mile-long monolith that sits in southeast Goiás state.
New satellite imagery from Landsat 9 shows the structure in vivid detail. The dark monolith is covered by the Cerrado savanna, a tropical ecosystem that blankets about a quarter of Brazil and is the second-most abundant biome in South America after rainforests like the Amazon. The Cerrado’s ability to soak up rainwater makes the dome function like a giant sponge, collecting water that percolates through the rock and refills underground reservoirs that feed the nearby hot springs.
The collected liquid refills submerged groundwater reservoirs. These reservoirs help feed the nearby hot springs with a steady supply of warm water, even during the region’s dry season.
The Dome’s Dark Monolith
The Caldas Novas dome is an oval structure about 12 miles long and 7 miles across. It sits in southeast Goiás state and towers above the surrounding flatlands. The dark color comes from the dense vegetation of the Cerrado, which covers the entire structure.
An optical illusion known as relief inversion can trick some viewers. From a distance, the raised land may appear as a bowl-like depression rather than a rising dome. The effect depends on lighting and perspective, so the structure looks different at different times of day.
The dome gets its name from the town of Caldas Novas, which is visible in the satellite image. The town sits between the dark-green dome and Lake Corumbá, an artificial reservoir created by a nearby hydroelectric dam. Caldas Novas is home to around 100,000 people, but it draws hundreds of thousands of visitors each year who come to bathe in the hot springs.
How the Sponge Feeds the Springs
The Cerrado savanna is much more ecologically diverse than most savannas. It mixes woodland, grassland and wetland in a single landscape. That diversity means the biome readily soaks up rainwater, which percolates through the monolith’s inner structure.
According to NASA’s Earth Observatory, the system keeps the springs flowing year-round.
The Cerrado is often called the “cradle of waters” in Brazil. Its role in recharging groundwater and feeding major rivers across the country makes it a vital source of fresh water for the nation. The dome itself helps feed several waterfalls around its edges.
The Hot Springs Are Not Volcanic
Unlike most thermal baths, the hot springs around Caldas Novas are not heated by volcanic activity. Instead, water within deep fractures in the rock is heated by Earth’s naturally higher temperatures at depth before it circulates back to the surface.
Many experts previously thought the monolith was formed by an ancient “magmatic intrusion,” in which molten rock burst through the planet’s crust. A 2021 study largely disproved that theory. The structure was most likely created by other geological processes.
The discovery changes how geologists understand the formation of such features. The magmatic intrusion idea had been widely assumed, but the new evidence points elsewhere.
Protecting the Cradle of Waters
The dome and its surroundings are protected as part of Caldas Novas State Park, which was established in 1970. The park is home to several unique species, including the red-legged seriema (Cariama cristata) birds, the pequi tree (Caryocar brasiliense) and the wolf’s plant (Solanum lycocarpum).
The park’s main purpose is to protect the Cerrado covering the dome. In recent decades, large swaths of the biome have been cleared across South America to make way for more agricultural land. The clearing resembles the deforestation that plagues the Amazon rainforest.
The satellite photo shows the issue clearly. The region surrounding the dome was likely once covered with the Cerrado, but it is now a patchwork of farms and fields. The contrast between the protected dome and the cleared land is stark, and it illustrates the pressure the biome faces across Brazil.
What the Satellite Shows
The Landsat 9 image captures the full scale of the structure. The dark green of the Cerrado stands out against the lighter ground around it, creating a striking visual contrast. The town of Caldas Novas appears in the image.
The photo was taken on May 19, 2025. It shows the dome in its natural setting, surrounded by the savanna that defines the region. The image is part of a series of Earth from space photos published by NASA’s Earth Observatory.
The Cerrado’s role as a water collector is visible in the landscape. The dome acts as a natural reservoir, and the result is a steady supply of warm water for the hot springs.
Related Stories From Earth From Space
The Caldas Novas dome is not the only striking feature captured from orbit. NASA’s Earth Observatory has published a series of images showing unusual landscapes around the world.
A 2015 satellite photo showed a series of golden tendrils surrounding Ghana’s Lake Bosumtwi. The lake and its surroundings were shaped by a massive meteor impact around 1 million years ago. The image revealed the scars left by the collision.
A 2024 satellite photo showed a series of ephemeral lakes that merged into a single emerald structure in Australia’s Northern Territory. The merger followed two years of extreme rainfall, which filled the normally dry basins. The image captured the moment when separate lakes became one.
A 2021 astronaut photo showed the surprising similarities between Mount Sundoro and Mount Sumbing, which lie at the heart of Java, Indonesia. The two volcanoes share a distinctive shape, with steep slopes and sharp peaks that look nearly identical from above.
The Image as a Reminder
The satellite photo is a reminder of what is at stake. The contrast between the protected dome and the cleared land shows the tension between conservation and development. The dome stands as a symbol of what the Cerrado can offer.
The Caldas Novas dome is a remarkable structure, and the satellite image shows it in all its glory. The Cerrado savanna that covers it is a unique ecosystem, and its ability to collect water is a natural wonder. The hot springs that draw visitors are a sign of the land’s power.
The dome is a place of beauty and of mystery. It is a place where nature works in ways that defy easy explanation. The Landsat 9 image captures that mystery, showing the dome as it is today.
The future of the dome is uncertain, but the image gives us hope. It shows the dome in all its glory, surrounded by the savanna that gives it its name. The Cerrado is the cradle of waters, and the dome is its crown.
The dome is a natural wonder, and the Cerrado is its foundation. Together, they create a place of beauty and of mystery. The Landsat 9 image captures that mystery, showing the dome as it is today.
Source material: “Towering 'sponge' dome in Brazil is the secret source of nearby hot springs,” Live Science.
Get the Notebook.
The day's best stories and every fresh verdict, in plain English, in your inbox by seven. One email a day, no more.