Pisa sacked the Tunisian city of Mahdia in 1088. Four years later, Pisan and Genoese ships helped Alfonso VI of Castilla to push El Cid out of Valencia. A Pisan fleet of 120 ships also took part in the First Crusade, and the Pisans were instrumental in the taking of Jerusalem in 1099. On their way to the Holy Land, the ships did not miss the occasion to sack some Byzantine islands; the Pisan crusaders were led by their archbishop Daibert, the future patriarch of Jerusalem. Pisa and the other took advantage of the crusade to establish trading posts and colonies in the Eastern coastal cities of the Levant. In particular, the Pisans founded colonies in Antiochia, Acre, Jaffa, Tripoli, Tyre, Latakia, and Accone. They also had other possessions in Jerusalem and Caesarea, plus smaller colonies (with lesser autonomy) in Cairo, Alexandria, and of course Constantinople, where the Byzantine Emperor Alexius I Comnenus granted them special mooring and trading rights. In all these cities, the Pisans were granted privileges and immunity from taxation, but had to contribute to the defence in case of attack. In the 12th century, the Pisan quarter in the eastern part of Constantinople had grown to 1,000 people. For some years of that century, Pisa was the most prominent commercial and military ally of the Byzantine Empire, overcoming Venice itself.