Intrepid divers don scuba attire to descend into deep subterranean caverns, exploring an underwater paradise of giant rock formations and chambers huge enough to fit hundreds of buses, while catching glimpses of rare species that only live in this submerged realm. This might sound like an adventure out in the open sea in a faraway land, but such subaquatic excursions are happening right beneath the streets of urban Budapest, where the city’s cherished thermal waters have carved out a pleasantly warm underwater cave system – and now a new video reveals what’s down in the deep below our feet.

Budapest has no shortage of hot sensations. Lying atop a vast network of healing spring waters circulating underground, the city is internationally esteemed for its thermal spas that provide natural benefits for soakers – but these subterranean hot springs also create numerous cave systems found around town, including the easy-to-traverse Szemlő-hegyi Cave or the Pál-völgyi Cave, a coveted destination for spelunkers. However, one of the most exciting formations of this far-reaching system is the Molnár János Cave, an obscured haven for scuba divers found directly beneath the Magyar metropolis.

Great Big Story, a global media company devoted to cinematic storytelling, has recently published a mini-movie that reveals what makes the Molnár János Cave an in-demand destination for adventurers of the deep. This underwater site was discovered in the 19th century by János Molnár, who traced the warm spring water from the lake outside Buda’s St. Lukács Bath to its source beneath the city, and after decades of expeditions have successfully charted many of its caverns, this maze of tunnels became a semi-hidden destination for divers who descend into pitch-dark conditions to discover a concealed world of oversized rock formations and rare species that live only in this pleasantly warm site, with water temperatures ranging between 20-28° Celsius. Flowing beneath an urban area with paved roads and buildings, a rope network helps underwater explorers find their way back to the water’s surface where they plunged in.

The cave is ordinarily open for divers, with the MJ Cave association organizing guided descends, but – according to the organization’s Facebook page – due to ongoing construction works around the area, plunging activities are currently suspended through October 1st.