
Pilgrims praying at the Haram mosque in Makkah. In this mosque is the Kaaba (the black building in the picture) which Muslims turn toward when praying. The Kaaba is the place of worship which God commanded the Prophets Abraham and his son, Ishmael, to build
The rites of the Hajj include circling the Kaaba seven times and going seven times between the hillocks of Safa and Marwa, as Hagar did during her search for water. Then the pilgrims stand together in Arafa5 and ask God for what they wish and for His forgiveness, in what is often thought of as a preview of the Day of Judgment.
The end of the Hajj is marked by a festival, Eid Al-Adha, which is celebrated with prayers. This, and Eid al-Fitr, a feast-day commemorating the end of Ramadan, are the two annual festivals of the Muslim calendar.
(http://www.islam-guide.com/frm-ch1-1.htm)