The basilica is built on the site of a much older Byzantine church, and the remains of the Byzantine mosaic floor can still be seen in the courtyard, protected under glass.
More mosaics decorate the interior of the abbey, including a lush illustration of the Zodiac symbols. Another mosaic above the high altar depicts the Madonna and Child.
Nearby on Mount Zion is the Room of the Last Supper, a room comprised of centuries-old vaulted ceilings, where the Last Supper is said to have taken place. Also nearby is David's Tomb, though it's unlikely that King David was in fact interred there.