The western or outer front is flanked on each side by a projecting wing, with a row of three smaller Doric columns between Antae at right angles to the main portico.
The west end was formed by a wall, on which stood four columns between antae; but the main entrance to this western compartment was through a large and very ornate doorway on the north; and a large Ionic portico, consisting of four columns in the front, and one in the return on each side, was placed in front of this door.
A small Ionic temple of marble with two caryatids between antae stood on this substructure.
On a parapet at the rear of each chamber a single slender Ionic column between two antae supported an Ionic entablature.
In it were carved out four chambers or reservoirs all connected and a porch consisting of three pillars between two antae in which the side walls ended.