The last place we went to during our daytrip to Ravenna was the Basilica di Sant'Apollinare Nuovo which also houses amazing mosaics.
This basilica fits the more conventional appearances of a church being a more rectangular shape than circular. It was gorgeous, and again the outside does not do the inside justice.
The mosaics inside are huge, and they were done by multiple people working at the same time.
It was comissioned for the emperor Theodoric depicting religious martyrs on one side and his palace on the other. The altar area looks as if it doesn't belong inside this basilica since it doesn't have any mosics in it at all and is decorated in a completely different style from the rest of the church. It is adorned by frescoes and ceramics on the walls and ceiling instead of mosaics.