Naturally formed caves under piled up boulders or in the steep rock face of the mountains as refuge for rishis and monks were known in India since very ancient times.

In the 2^nd century BC Buddhists began to carve planned temples and monasteries into the rocks and gave them the shape of their structural architecture their chaityas, viharas and stupas.

Soon the Hindus followed and carved temples with pillared halls and rectangular sanctuaries into the mountains.   

This fascination for worshipping God in the heart of the mountains inspired men to extraordinary architectural achievements.