Baradla cave, Limestone cave system in Aggtelek National Park, Hungary and Slovak Karst, Slovakia

Baradla Cave is a limestone cave system in the Aggtelek Karst of northern Hungary, extending over 25.5 km and including the 5.3 km Domica Cave in Slovakia. Its meandering main channel runs about 7 km, on average 10 m wide and 7 to 8 m high, with a cavern large enough to hold 1000 people. The system holds the world's largest known stalagmite, 37.2 m tall.

Natural entrances to Baradla have been open since ancient times, with traces of Neolithic occupation inside. The first written mention dates from 1549, and Joseph Sartory carried out the first survey in 1794. In 1825 the engineer Imre Vass explored a further 5 km of the main branch and published an accurate map and description in Hungarian and German in 1831.

The cave has a concert hall fitted with a stage, set against a field of stalactites lit by concealed lighting; concerts of every musical style are held there, and the hall is shown during guided tours. Parts of the cave were once navigated by boat, no longer possible because the water level is too low.

Visitors can enter the cave through several entrances located on both the Hungarian and Slovak sides of the cave system. Expert guides lead tours of varying lengths depending on visitor interest and fitness level.

The cave system is home to more than 500 species of cave-dwelling animals, including 21 bat species adapted to living in darkness. This animal community makes it one of the most biologically diverse underground habitats in Europe.