By the end of Late Antiquity, Athens had shrunk due to sacks by the Herulians, Visigoths, and Early Slavs which caused massive destruction in the city. In this era, the first Christian churches were built in Athens, and the Parthenon and other temples were converted into churches. Athens expanded its settlement in the second half of the Middle Byzantine Period, in the 9th to 10th centuries AD, and was relatively prosperous during the Crusades, benefiting from Italian trade. After the Fourth Crusade the Duchy of Athens was established. In 1458 it was conquered by the Ottoman Empire and entered a long period of decline.