Caves of Aggtelek and Slovak are located on the north-eastern border of Hungary and the south-eastern border of Slovakia. They are about 2 million years old and spread in an area of 600 km2. These caves topographically comprise limestone plateaus dissected by deep river valleys. It is a rare combination of karst formation due to both tropical and glacial climatic effects. It has a most significant cave system named Baradla-Domica, which is a cross-border network richly decorated with stalagmites and stalactites.