The Frankish leader Guillaume de Villehardouin built the fortress in 1249. When the Byzantines won back the Morea from the Franks, Emperor Michael VIII Palaeologos made Mystras its capital and seat of government. Settlers from the surrounding plains began to move here, seeking refuge from the invading Slavs. From this time until Dimitrios surrendered to the Turks in 1460, a despot of Morea (usually a son or brother of the ruling Byzantine emperor) lived and reigned at Mystras.
While the empire plunged into decline elsewhere, Mystras enjoyed a renaissance. Gemistos Plethon (1355–1452) founded a school of humanistic philosophy here and his enlightened ideas, including the revival of the teachings of Plato and Pythagoras, attracted intellectuals from all corners of Byzantium. Art and architecture also flourished, as seen in the town's splendid buildings and frescoes.
Mystras declined under Ottoman rule, but thrived again after the Venetians captured it in 1687 and developed a flourishing silk industry. The population swelled to 40,000. The Turks recaptured the town in 1715 and from then it was downhill all the way; it was burned during the Orlov uprising in 1770 and Ibrahim Pasha torched what was left in 1825. By the time of independence it was a largely abandoned ruin, and the refounding of nearby Sparta in 1834 contributed to the decline, though Mystras remained inhabited until 1953. Much restoration has taken place since the 1950s (and continues to this day) and in 1989 it was declared a Unesco World Heritage site.