It measures, at the level of the steps which surround it, more than 40 m in length and nearly 30 m in width, and it had, galleries (porticos), today missing, along its North, West and South facades. These galleries opened on the outside by an arcade on colonnade (16 fragments of the barrels of these columns lie on the site, most to the north of the basilica, together with many other beautifully carved stones.