The Byzantines built several great palaces in Constantinople and this is the only one to survive almost intact. It's from the late 13th century, in typical alternating marble and red-brick rows, and was an imperial residence: Porphyrogenitus means "born to the purple" indicating the heir to the crown. Yet it was merely an annex or pavilion within the much greater Palace of Blachernae, of which nothing else remains. It's set within the north end of the Theodosian Walls and was much bashed during the Ottoman capture. Later it was variously a menagerie, brothel, pottery, poorhouse and bottle works, then fell derelict in the 20th century. In 2021 it re-opened as a museum.