Although there is not much left of the once Great Palace of the Byzantine emperors in Istanbul, there are some incredible mosaics from one of the peristyle courtyards. The mosaics are displayed in the Istanbul Mosaic Museum (Istanbul Buyuk Saray Mozaikleri Muzesi) They are thought to be from 5th century AD but unfortunately not much is known about the iconography. They are a visual delight all the same.
Istanbul Buyuk Saray Mozaikleri Muzesi
(It is right in the Shopping Bazaar Arasta behind the Sultanahmet mosque)