The ground plan of the palace is an irregular rectangle with towers projecting from the western, northern, and eastern facades. It combines qualities of a luxurious villa with those of a military camp, with its huge gates and watchtowers. The palace is enclosed by walls, and at times, it housed over 9000 people. Subterranean portions of the palace feature barrel vaulted stonework.

Only the southern facade, which rose directly from, or very near to, the sea, was unfortified. The elaborate architectural composition of the arcaded gallery on its upper floor differs from the more severe treatment of the three shore facades. A monumental gate in the middle of each of these walls led to an enclosed courtyard.

The southern Sea Gate was simpler in shape and dimensions than the other three. Perhaps it was originally intended as the emperor's private access to boats, or as a service entrance for supplies. The dual nature of the architectural scheme, derived from both villa and castrum types, is also evident in the arrangement of the interior. The transverse road (decumanus) linking the east and west gates divided the complex into two halves. In the southern half were the more luxurious structures; that is, the emperor's apartment, both public and private, and cult buildings.

The emperor's apartment formed a block along the sea front. Because the sloping terrain created large differences in level, this block was situated above a substructure. Although for many centuries almost completely filled with refuse, most of the substructure is well preserved, giving us evidence as to the original shape and disposition of the rooms above.