Here's why:

* Apollo's Oracle: At the summit of Mount Parnassus was the famous Oracle of Delphi, dedicated to Apollo.

* Muses' Home: The Muses, the goddesses of the arts and sciences, were said to have their home on Mount Parnassus.

* Castalian Spring: The Castalian Spring, a source of inspiration and poetic creativity, flowed from the slopes of Mount Parnassus.

Therefore, Mount Parnassus is deeply associated with both Apollo and the Muses in Greek mythology.