The city's foundation has traditionally been ascribed to the Byzantine Emperor Justinian in the 6th century AD, but modern archaeological research has uncovered evidence of Hellenistic settlements. Ioannina flourished in the late Byzantine period (13th–15th centuries). It became part of the Despotate of Epirus following the Fourth Crusade and many wealthy Byzantine families fled there following the sack of Constantinople, with the city experiencing great prosperity and considerable autonomy, despite the political turmoils. Ioannina surrendered to the Ottomans in 1430 and until 1868 it was the administrative center of the Pashalik of Yanina. In the period between the 18th and 19th centuries, the city was a major center of the modern Greek Enlightenment. Ioannina was ceded to Greece in 1913 following the Balkan Wars.