In India the state Meghalaya is referred as Mecca for universal cavers. Every year various cave lovers visit this region and participate in International Cave expedition Program. Till date more than 1000 km subterranean passages has been mapped only from this region.
Read about the The Longest and Deepest Caves of Indian Subcontient, in the Features' section of of Ambient Science Volume 1(2) .
http://www.caves.res.in/journal/c.htm