The Barabar Caves are the oldest surviving rock-cut caves in India, mostly dating from the Mauryan period (322–185 BCE), and some with Ashokan inscriptions, located in the Jehanabad District of Bihar.
These caves are situated in the twin hills of Barabar (four caves) and Nagarjuni (three caves) - caves of the 1.6 km distant Nagarjuni Hill sometimes are singled out as Nagarjuni Caves.
Web : http://en.wikipedia.org/wiki/Barabar_Caves