By the late fifth century Constantinople had grown into a dense metropolis of 200,000 to 300,000 residents. The immense investment lavished on it showed in a sophisticated network of public facilities, some of which carried over into the Ottoman city and have survived to this day: the Hippodrome built by Constantine as the main city square, the aqueduct constructed by Emperor Valens in 368, the subterranean water cisterns, and the land walls erected by Theodosius II in the fifth century. The Theodosian fortifications remained the western boundary of the city all the way to the twentieth century. The Great Palace built by Constantine next to the Hippodrome remained the official residence of the Byzantine emperors until the mid-thirteenth century. The elaborate ceremony and modes of statecraft that characterized the luxurious court influenced Muslim states in the Mediterranean region, including the Ottoman Empire.