The Augustaion or, in Latin, Augustaeum, was an important ceremonial square in ancient and medieval Constantinople (modern Istanbul, Turkey), roughly corresponding to the modern Aya Sofya Meydani (Turkish, "Hagia Sophia Square"). Originating as a public market, in the 6th century it was transformed into a closed courtyard surrounded by porticoes, and provided the linking space between some of the most important edifices in the Byzantine capital. The square survived until the late Byzantine period, albeit in ruins, and traces were still visible in the early 16th century.