Nagarjuni Hills are located 35km north of Gaya, less than two km from Barabar Hills in Jehanabad district in Bihar.
Three caves were excavated in the Nagarjuna Hills – the Vadathi-ka-Kubha, the Vapiya-ka-Kubha, and the Gopi-ka-Kubha. An important archaeological site, it has been grossly ignored.
The Nagarjuna caves bear inscriptions of Ashoka and his grandson Dasaratha which are helpful in determining the dates of construction and religious affiliations of the residents. Dasharatha, is known to have dedicated three caves in the Nagarjuni Hills to the Ajivika sect.
Source:
http://www.indiantravelportal.com/bihar/caves/nagarjuna-caves.html
http://buddhistcircuitbihar.com/jehanabad.htm
http://insiderblogs.info/peshhery-barabar-barabar-caves-g-gaya-shtat-bikhar-in/