Son Bhandar Caves situated at Rajgir, Nalanda in Bihar state. Son bhandar group of caves has two caves known as eastern and western cave. Son bhandar caves are concerned with Jainism and considered to belong to 3-4 century AD. These caves were first inspected by cunninghum and he concluded to have analogy with saptparni caves of Buddhism creed. After cunninghum several scholars visited this place and some had opinion to concern with Buddhism. After some time all Buddhism connections were refused because of an inscription found on the southern wall of a cave. According to this inscription these caves were built by inspiration of a Jain muni Vair for Jain ascetics. Sculptures of Teerthankaras were also carved in these caves. From architectural aspect; these caves are analogous to Nagarjuni cave and Barbar caves of Mauryan era. Therefore it can be concluded that construction time should not be much differ from above mentioned caves. These caves should be related to digambar sect of Jainism as Xuanzang wrote in his book about Vaibhar hill of rajgir that the place was occupied by Digambar Jaina monks for meditation purpose. After some centuries these caves were converted by Hindus as Lord Vishnu sculpture was also found from mound of a cave.
It is the western cave which gave the name to monument: Son Bhandar means "store of gold" and legend about this treasure is linked to western cave.
The cave believed to be a guard cave – contains single rectangular chamber, 10.4 x 5.2 m large. The vaulted ceiling stands stands on vertical walls, vault rises up to 1.5 m high. This resembles the style of older Mauryan rock-cut sanctuaries. In ancient times most likely there was a roofed verandah in the front of caves.
Walls, doorjambs and front wall contains numerous epigraphs. Small image of standing Vishnu is etched on the left side of doorway this possibly testifies that caves were taken over for Hindu worship. Local legend tells that the this cave still hides a passage to the treasury of gold entrance in this passage is well hidden in the cave chamber behind an ancient stone wedge. Some also believe that the passage goes through Vaibhargiri mountain and reaches Saptaparni Caves on the other side of range. Some believe that this treasure belongs to Jarasandha, others that to Bimbisara. In a case of Bimbisara legend goes that when Ajatashatru confined his father Bimbisara (remnants of this prison are nearby), his mother secretly hid some wealth and later donated it to Tirthankar.
In the wall of cave there is seen a trace of carving, resembling a doorway and next to it – an undeciphered inscription in Sankhlipi writing or shell script. It is believed that this inscription is a password who will read it, will open the door and enter the passage. This ornate script has been found in India as well as in Java and Borneo and never been deciphered. There is also a black mark above or in the upper part of the mysterious doorway is of left by cannonball when Brits tried (without success) to break the wall and enter the passage.
Eastern cave is partly ruined – front part of cave chamber has fallen. Upper floor above the cliff made in brick is added later, during Gupta period and possibly caused the collapse of front wall of the cave. Most likely also this cave had verandah in front. Southern wall of this cave contains important early Jain artwork – exquisitely sculpted small reliefs of six Jain Tirthankaras – Padmaprabh, Parsvanath, Mahavira and others. This relief seems to be added later, some time after the completion of caves, it shows little congruity with the plan of rock-chamber.