Jabal al-Hira (Arabic: جبل الحراء) is a mountain which lies about two miles from the Ka’bah. Near the top is a small cave known as the Cave of Hira (Arabic: غار حراء), which is a little less than 4 meters in length and a little more than 1.5 meters in width. It was here that the Prophet Muhammad (ﷺ) received the first revelations of the Holy Quran during the month of Ramadhan in 610 CE. The mountain is also known as Jabal al-Noor (the Mountain of Light) and Jabal al-Islam (the Mountain of Islam).

• The Prophet (ﷺ) first began to have revelations in the form of good dreams which came true. Then he began to like solitude. He would go to the cave of Hira and meditate there in solitude for a number of days and nights. He would take provisions with him to stay for an extended period, and when he returned to Khadija (رضي الله عنه), he would stock up again and go back to the cave. This was his practice until Truth was revealed to him by an angel while he was in the cave of Hira.

Source: islamiclandmarks.com