Gruta do Lago Azul is a cave 20 km from the center of Bonito-MS. It was registered by  of National Historical and Artistic Heritage in 1978, and is inscribed in three of Tombo’s four books, the ethnographic, landscape and archaeological

Discovered by an Indian Terena in 1924, the cave has in its interior a blue lake with dimensions that make it one of the largest flooded cavities on the planet.

After a descent of 100 m, you come across a lake with intensely blue waters, whose depth is estimated to be 90 m. With its geological formations – not only the roof but also the floor of the cave of various shapes and sizes – it attracts the attention of tourists and researchers from all over the world. No one knows for sure where their waters come from, it is believed that there is an underground river that feeds the lake.