View looking northwest at the northern and western walls of the hall. Note the finely finished stones in both walls as well as the chest high decorative horizontal ridge/railing that separates the lower and upper portion of the walls. Near the corner of the west (left) wall note the delicately carved protruding pilaster.
I visited this all in the 1970’s with Gabi Barkai and I thought he said it might be Hasmonean. But our guide said it was Herodian (37–4 B.C.) with possibly some Hasmonean elements.
I am not sure of its function but it certainly is “monumental.” In my Zondervan Atlas of the Bible I labeled it as a “Public Building” (p. 250).
The original hall was presumably part of a large Herodian public building that some scholars have identified with the Chamber of Hewn Stones (the Xystos) or with the Council Building, both referred to by Josephus as being in this area (War V, 144).
From The New Encyclopedia of Archaeological Excavations in the Holy Land vol. 2, p. 742.