Sonbhandar caves also referred as Swarn Bhandar are believed to be the historical fortune of the Rajgir city. These caves are located on the north-west side of Maniyar Mutt, Rajgir City in Bihar, India. These caves are also known for their historical eminence and are visited by tourists as a part of their trip to Rajgir. The wall inscriptions add even more to the popularity of these caves.
Sonbhandar caves are a set of dual chambers that were interestingly hollowed out from a single colossal rock. It is also believed that one of these chambers was used as the guard room containing an entry leading to King Bimbisara Treasury. This treasury is, however, still believed to be intact.
Architecture
The Sonbhandar caves can be divided into two segments – the Western Cave and the Eastern Cave. The Western cave is seen as the guard room, containing a single chamber with rectangular shape sized 10.4 x 5.2m. The arched ceiling is standing on vertical walls with the vault being as high as 1.5m. This reflects the ancient Mauryan style of rock cut sanctuaries. In historical times, there may probably be the trend of keeping roofed verandahs in front of the caves.
Contrastingly, the Eastern Cave is partially ruined with the front part have been fallen down. However, the upper floor over the cliff finished in brick was added later, in the Gupta epoch thus leading to the falling down of the cave. The second chamber also includes some of the traces of standing and seating engraved into the outer wall.
Cave Icons/Sculptures
The southern wall of the caves carries six miniature figures of Jain Tirathankaras also including Parswanatha, Padmaprabha, and Mahavira as well. Also, the walls of the Sonbhandar caves contain inscriptions in the shell script or Sankhlipi and are also believed to throw clues to open the entryway for the treasure. This secret entry door also contains a black mark, in its upper section, that occurred as a result of unsuccessful attempt made by Brits to break the wall when trying to enter this passage.
Source:
http://www.indiamapped.com/caves-in-india/bihar-sonbhandar-caves/