The Ka'bah, a shrine believed to have been originally built by the prophet Abraham as the first House of God, is a focal point in the daily lives of Muslims who turn in its direction each time they pray. Calculating the direction of the Ka'bah was therefore an important challenge that required Islamic scientists to make astronomical observations with such complex instruments as astrolabes and, in later times, specially adapted compasses. These instruments were also used for accurate timekeeping, so that daily prayers could be performed at the correct times. Knowledge of astronomy and other sciences has therefore been esteemed in the Islamic world, and medieval Muslims played a key role in preserving and developing the scientific heritage of classical antiquity. This knowledge came to be shared by Christian and Jewish people in Europe and formed the foundation from which modern science arose.