What is the Ka`ba? The Ka`ba is the place of worship which God commanded Abraham and Ishmael to build over four thousand years ago. The building was constructed of stone on what many believe was the original site of a sanctuary established by Adam. God commanded Abraham to summon all mankind to visit this place, and when pilgrims go there today they say 'At Thy service, O Lord', in response to Abraham's summons. Who is Muhammad? Muhammad, was born in Makkah in the year 570, at a time when Christianity was not yet fully established in Europe. Since his father died before his birth, and his mother shortly afterwards, he was raised by his uncle from the respected tribe of Quraysh. As he grew up, he became known for his truthfulness, generosity and sincerity, so that he was sought after for his ability to arbitrate in disputes. The historians describe him as calm and meditative. Muhammad was of a deeply religious nature, and had long detested the decadence of his society. It became his habit to meditate from time to time in the Cave of Hira near the summit of Jabal al-Nur, the 'Mountain of Light' near Makkah. How did Muhammad become a prophet and a messenger of God? At the age of 40, while engaged in a meditative retreat, Muhammad received his first revelation from God through the Angel Gabriel. This revelation, which continued for twenty-three years, is known as the Quran. The Mountain of Light where Gabriel came to Prophet Muhammad. As soon as he began to recite the words he heard from Gabriel, and to preach the truth which God had revealed to him, he and his small group of followers suffered bitter persecution, which grew so fierce that in the year 622 God gave them the command to emigrate. This event, the Hijra, 'migration', in which they left Makkah for the city of Madinah some 260 miles to the north, marks the beginning of the Muslim calendar. After several years, the Prophet and his followers were able to return to Makkah, where they forgave their enemies and established Islam definitively. Before the Prophet died at the age of 63, the greater part of Arabia was Muslim, and within a century of his death Islam had spread to Spain in the West and as far East as China. The Prophet's Mosque, Madinah, the dome indicates the place where his house stood and where he is buried. How did the spread of Islam affect the world? Among the reasons for the rapid and peaceful spread of Islam was the simplicity of its doctrine - Islam calls for faith in only One God worthy of worship. It also repeatedly instructs man to use his powers of intelligence and observation. Taj Mahal, India. Hui Shen Mosque, China, Built in the 7th Century. Within a few years, great civilizations and universities were flourishing, for according to the Prophet, 'seeking knowledge is an obligation for every Muslim man and woman'. The synthesis of Eastern and Western ideas and of new thought with old, brought about great advances in medicine, mathematics, physics, astronomy, geography, architecture, art, literature, and history. Many crucial systems such as algebra, the Arabic numerals, and also the concept of the zero (vital to the advancement of mathematics), were transmitted to medieval Europe from Islam. Sophisticated instruments which were to make possible the European voyages of discovery were developed, including the astrolabe, the quadrant and good navigational maps.