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.
Wood was also used for all the columns, doorposts, and antae (rrapacrTetScs), and in some cases the walls of the rooms were lined with wood, carefully fixed by dowels, the holes for which still exist.
There are still standing nine columns of the south side and two of the north of the peristyle, and one of the antae and an inner column of the pronaos.
The most remarkable architectural feature of the building is the partition that separated the altar from this long gallery; it consists of two columns between antae, with capitals of a very peculiar form, consisting of the fore parts of bulls set back to back; from these the whole building is sometimes called the sanctuary of the bulls.