Located about 25 KMs from Gaya, Barabar Hills have India's oldest surviving rock-cut caves called Barabar Caves. The Barabar caves probably belong to the Mauryan period and were believed to be used by Buddhist monks. The architecture of these extraordinary caves is fairly unique and is famous for the echo effect in the inner chamber. There are four caves in the hills, Karan Chaupar, Lomas Rishi, Sudama and Visva Zopri. The Nagarjuna hills nearby also has three such caves.