The birthplace of the prophet Mohammed, and the destination for the largest Muslim pilgrimage centre, the town of Mecca is forbidden to non-Muslims. The pilgrimage forms part of the Five Pillars of Islam, and every adult Muslim who is healthy in body and spirit should go there at least once in his lifetime. The Hadj (pilgrimage, in Arabic) allows the release from sin. Its practice and rites were defined by Mohammed himself. First of all there are a certain number of stops to make, in the surrounding sites. Men wear two pieces of white unsown (ihram) fabric, sandals, with their head bare, that they shave partially or wholly. Women should cover their hair with a scarf. The main stages of the Hadj include seven circumambulations around the Kaaba, in the enclosed area of the Great Mosque. The pilgrim should also pray at 'Abraham's place' and stand from midday to midnight at Arafat, 15 miles from Mecca. Celebration of the Sacrifice (Eid-ul-Adha) takes place at Mina, by Mecca, on the 10th of the last Muslim month. After the ceremony, which is dedicated to the stoning of the pillars symbolising Satan, the pilgrim has a final circumambulation in the Great Mosque. Located at the centre of the Great Mosque of Mecca, the Kaaba is also the place the Muslims converge on after the five daily prayers. This 'cube', 49 ft high and 39 ft wide, contains the Black Stone in its north-western corner, completely covered by a veil. It was already a pilgrimage centre for the polytheist religions of Arabia well before the beginning of the Islamic period, but Mohammed made it the most important pilgrimage centre of Islam.