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

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 entrance to the cave s