Al-Aqsa means "the furthermost." Muslims believe that Muhammad was transported from the Sacred Mosque in Mecca to al-Aqsa and then up to heaven on a mythical creature during what is called "the Night Journey."
This was the second Muslim house of prayer built after the one in Mecca, and was the original direction of the qibla, the direction towards which Muslims pray, until Muhammand announced that God directed him to turn towards the Ka'aba.
The Al-Aqsa mosque served as the residence of the Latin King of Jerusalem during the Crusades, and was thought then to be the Temple of Solomon. In 1131 it was given over to an order of soldier-monks founded a decade earlier; from their residence here that order became known as the Knights Templar.