The complex is raised high on a walled platform, with five "palaces" or halls of varying size, and grand entrances. The function of Persepolis remains quite unclear. It was not one of the largest cities in Persia, let alone the rest of the empire, but appears to have been a grand ceremonial complex that was only occupied seasonally; it is still not entirely clear where the king's private quarters actually were. Until recent challenges, most archaeologists held that it was especially used for celebrating Nowruz, the Persian New Year, held at the spring equinox, and still an important annual festivity in modern Iran. The Iranian nobility and the tributary parts of the empire came to present gifts to the king, as represented in the stairway reliefs.