I agree with other observations on this thread that we in the West have tended to neglect study of the Empire after the fall of Rome. Whatever it’s called, I find it a fascinating world, lost to the predations of the barbarians from deserts and steppes. I also agree with the observation that by the time the Venetians sacked Constantinople the Empire was really not an Empire anymore. But, if you want to see some of the most beautiful objects from old Constantinople, they can be found in St. Marks, Venice.
Early in the 1960s the excavation of the post-Roman settlement at Cadbury in England uncovereddark ages chocolatepottery and glass etc from Constantinople. The seagoing trade was robust in the heyday of the Roman Empire, but it continued to be strong, eventually surpassed by the successor states in the former western provinces.