A view of two of the eight towers of Castel del Monte, a 13th-century citadel and castle situated in Andria (Apulia region, southeast Italy). It stands on a promontory, where it was constructed during the 1240s by the Emperor Frederick II. Castel del Monte's geometric design was unique: the fortress is an octagonal prism with an octagonal tower at each corner. Both floors have eight rooms and an eight-sided courtyard occupies the castle's centre. prism tower eight