Miles from the ocean, there's diving beneath the streets of Budapest

Summary

Facebook Tweet Email Link Budapest — Every day, crowds flock to the Lukács Thermal Baths in Budapest, soaking in warm mineral-rich pools as yellow trams clatter along Frankel Leó Street. Most never suspect that just yards away, beneath the city’s historic streets, lies a hidden world: a vast underwater cave system heated by geothermal springs. From its entrance, tucked into the base of Rózsadomb — Rose Hill — an affluent neighborhood of elegant villas and tree-lined streets, the Molnár János Cave stretches for over 3.6 miles (5.8 kilometers) and plunges nearly 300 feet (90 meters) below the surface. Flooded with crystal-clear water at the temperature of a warm bath, it is one of the largest active thermal water caves in the world, and among the rare few open to certified cave divers. The way into the cave is easy to miss from the street. Next to a rocky limestone cliff, a small lake covered with lilies and algae glistens beside a crumbling 19th-century building that resembles an Ottoman bathhouse. On the firewall next to it, a mural of a diver hints at the secrets below. Through a gate, past an old bathhouse — once one of Hungary’s first concrete structures — a narrow alley leads to an unmarked doorway in the cliff. Above it, a sign reads “Happiness Factory,” flanked by smiling emojis. Once inside the brick-lined entranceway, the temperature rises with the geothermal heat. Diving gear lines the corridor. At the end, behind a drawn curtain, a stairwell drops into a rocky entrance where black waters wait in the gloom. Here, divers step into the warm water, their headlamps piercing through the darkness as they descend into a silent, shimmering world. Budapest is famous for its ornate bathhouses and spas, but its thermal waters have done more than soothe muscles and ease ailments. Over millennia, the same geothermal activity that feeds the city’s baths has carved a network of more than 200 caves beneath its streets — as mineral-rich springs slowly dissolved the surround...