Deep beneath the city – Exploring Budapest’s Underwater Cave System

Budapest is known worldwide for its unique spa culture with more than a hundred thermal water springs originating from the volcanic earth below. Less known is that behind the spring of Molnár János lies one of the most extraordinary cave systems in the world. It is a doorway to a hidden underwater world open for well-trained cave divers.

words & photographs by Michael Biach

Cave Diver in Molnár János.

Budapest is divided by the river Danube into two parts. The hills of Buda are situated on the west bank while Pest is on the flat east side. The cave system of Molnár János is located in the old town of Buda. Its healing thermal waters have been used for centuries and flow into a little pond called Lake Malom (malom means mill in Hungarian). Divers have found Roman constructions on the ground of the lake. Long time nobody knew where the water was coming from. In the 19th century an enthusiastic pharmacist named János Molnár started to investigate the dry areas of the cave and analysed the water of the spring. He was the first to think that there might be a huge underwater cave system under the Buda hills. First underwater explorations started in the 1950s, in the 70s and 80s divers successfully explored and charted 400 meters of the underwater cave. In 2002 a new passage and a whole new cave system were found after divers drilled through a wall into a huge chamber. Today several kilometers of the caves have been explored.

Today scientists regularly explore the cave, mapping the system and analyzing water and mineral samples. Even three new species of the Niphargus have been found inside the warm thermal waters.

Molnár János is also open to well-trained cave divers from all around the world making it a once-in-a-lifetime experience as it is the only natural cave system beneath a metropolis.

Cave Diver in Molnár János.
Lake Malom with the remnants of an old Turkish bath.
Cave divers during a pre-dive briefing in Molnár János.
A cave diver is getting ready for a cave dive in Molnár János.
A new species of Niphargus (visible under ultra-violet light) has been found inside the cave.
The waters of Molnár János emerge into the nearby spas…
… and after a few hundred meters flow into the nearby Danube.


    • Even most inhabitants of Budapest do not know about the cave system. There is also another very interesting unnatural “cave system” in Kobanya, the citiy’s 10th district. It is possible to dive an old limestone mine that has been flooded with ground water after it has been abandoned. Maybe I will post a story about that in the future.

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