Located in the ancient city of Rajgir, the Son Bhandar Caves are two artificial caves about which little is known. They are noted for their polished surfaces, a common trait in ancient Mauryan artifacts, but rather unusual in cave temples.

One of the caves is believed to be from the time of the Mauryan Empire, which ruled South Asia from the late fourth to early second centuries B.C. The second cave, adjacent to it, has been largely destroyed, but some of its beautiful Jain sculptures remain intact. Inscriptions in Gupta script can be found at the cave's trapezoidal entrance, and it is thought to have been built for Jain ascetics to live in between the third and fourth centuries.

Son Bhandar means "store of gold," and legend has it that within the caves' walls is secreted a treasure beyond measure. The existence of secret passages is unconfirmed, and if such a thing exists, may have belonged to an ancient king, either Jarasandha or Bimbisara.

According to the legend, the door to the treasury will open when the right password is uttered. There are still ambiguous inscriptions in the caves, and it is believed that they could hold the key. Over the years, some treasure hunts have been carried out, though never successful.