The pillars are the most striking feature of the mosque/cathedral, and they were built, at least in part, from an ancient Roman temple on the site.
This is the ceiling over the area where the Islamic ruler would have prayed. Then, in the middle of the mosque, is the Catholic cathedral. The mosque/cathedral is surrounded by a high wall. Abby asked me why it was there, and I replied that, as with most walls, it was for protection - to keep the mosque safe from invaders. She sighed and said, "Sadly, it wasn't enough."