The “Apsidal Hall” was probably the last building on the north belonging to the palace. Assuming this, the boundary of the complex is identifiable with the wall preserved today at the northern edge of the archaeological site.
The hall was built on a notional north-south axis, with another magnificent building, the Basilica, at its southern end. Remains of this building are visible in the eastern section of the archaeological site in Navarinou Square. The “Apsidal Hall” had a southern orientation and its exterior initially had the form of a basilica, i.e. a rectangular hall with an apse on its northern side.
Its interior was divided into two rooms which opened onto one another: a rectangular vestibule and a large hall with two niches on its south side. On the north, it ended in a raised apse.
The hall was heated by means of hypocaust channels still preserved below its flooring. In the middle of the masonry of the apse, there was a vaulted opening (a furnace, praefurnium) where wood was burned to produce warm air. Parts of the two vertical clay pipes used to draw off smoke are preserved encased in the apse’s masonry.
Both of its rooms carried rich decoration which is fragmentarily preserved. Their walls had white and colored marble revetments, and their floors were covered in marble laid in the opus sectile technique (marble tiles of different colors fitted together to form geometric patterns).
In a later building phase, probably in the 6th century, another hall (A) was added south of the vestibule. Given that a large part of it is buried beneath the paving of A. Svolou Street, its length is not known.
This hall, which probably led to a peristyle courtyard had a mosaic floor and luxurious interior decoration. Its north wall bore mural painting to the height of the doorway. Fragments of the mural painting found in the excavation of the monument featured representations of delicate wavy tendrils and red florets. Above the wall painting, the wall was covered with a mosaic that carried a Latin inscription, fragments of which are preserved.
In 1939, east of the new hall (A) at the site of the modern building located at 25 Dimitriou Gounari Street, the remains of a room (10.4 x 10m.) with marble decoration were found. According to E. Dyggve, this room, the existence of which is confirmed by an excavation drawing preserved in the Ephorate’s Archives, was part of the Hippodrome’s imperial viewing box (kathisma).
Modern scholarly opinion maintains that the “Apsidal Hall” was a triclinium, that is, it was used for banquets and other ceremonies connected with the presence of the emperor and his retinue in the Hippodrome.