Original: According to recent scholarship based on a rare series of bronze coins and artifacts found in the region , the caves and their adjacent valley probably comprised a sovereign kingdom in Gandhara which maintained at least partial independence for almost 500 years , from c. 4th century AD to the 9th century AD .
Simplified: The Kashmir Smast caves are a series of natural limestone caves , artificially expanded from the Kushan to the Shahi periods , situated in the Babozai mountains in the Mardan Valley in Northern Pakistan .