The Kaaba, a large stone structure constituting a single room with a marble floor, lies at the heart of the Holy Mosque (al Masjid al Haram) in the Holy City of Makkah. The Kaaba is Islam's holiest building. It now stands some 60 feet high and each side is approximately 60 feet in length. The Kaaba is the focal point around which the Holy Mosque is built. The four walls of the Kaaba are covered with a black curtain (the Kiswah) which reaches to the ground and is fastened to the Shadharwan with copper rings. The door of the Kaaba is set in the south-east wall, about seven feet from the ground. Inside, there are pillars, which support the roof. The interior is furnished with many gold and silver lamps. On the inner walls, there are several bands of inscriptions which record the many repairs done to the Kaaba. The Holy Qur'an makes it clear that Ibrahim (Abraham) and his son Ishmael were the true founders of the Kaaba, together building the holy shrine dedicated to the worship of the one true God. Five times each day more than a billion Muslims around the world turn to face the direction of the Kaaba to offer their prayers to the one true God. It is also, of course, the focal point of the Hajj when, once each year, some two million pilgrims converge on the Holy City of Makkah. Set in the eastern corner of the Kaaba is the Black Stone (al-Hajar al-Aswad). The Black Stone predates the birth of Islam but now, set in gold, forms an integral part of the Kaaba. In the course of the pilgrimage, the Hajjis will kiss or touch the Black Stone, not because the Black Stone is holy in itself but because it was kissed by the Prophet Muhammad (peace be upon him). On the roof of the Kaaba is a gilt water spout (al-Masabb) which projects out from the north-west wall. Opposite the north-west wall of the Kaaba, but not joined to it, is a semi-circular wall (Al-Hateem) which is 5ft high and 3ft thick. This area is also known as Hijr Ishmael. To the north-east side of the Kaaba is the Maqam Ibrahim, a small kiosk of glass and metal topped by a small dome. In it is kept the stone on which Ibrahim stood while building the Kaaba. Nearly opposite the Black Stone, near the Maqam Ibrahim, is the well of Zamzam.