From Sahih Muslim (Hadith 3046):
Abdullah (b. 'Umar) reported that whenever Allah's Messenger (ﷺ) entered Mecca, he got down at Dhi Tuwa and spend the night there until he observed the dawn prayer. And Allah's Messenger (ﷺ) observed this prayer on a rough hillock, and not in the mosque which had been then built there, but to the lower side of it (the mosque) on a hillock
Reference: Muslim 3046