Why are Buddhist stupas said to be ‘stories on stone’?

Buddhist stupas are said to be ‘stories on stone’ due to the following reasons:

a. Every Buddhist Stupa has its own history.

b. The sculptures in the stupa depict different stories which were taken away from different text at that time.

c. Art historians have identified that the sculpture at Sanchi was a scene from the Vessantara Jataka. Historians have tried to understand the meaning of the sculpture by comparing it with textual evidence.