The propylaea, built by Xerxes I (518–465 BCE), was the monumental entrance to the palatial city of Persepolis. Its western entrance was flanked by two huge bulls, whereas the eastern side was protected by two lamassu, shown in this view looking northeast. These creatures, part-bull or lion, part-bird and part-human, are one of the most enduring symbols of the Assyrian Empire. For Porter they were ‘monstrous’ and unfamiliar; ‘but whatever be the real intention, in the bull-man, which is here planted in the ancient seat of the earliest monarchs of the East, in the gate of his palace, his attributes fully answer the general idea of an emblematic reference to a just sovereignty’ (Travels, p. 593).