A cross of this sort, also known as an ‘enkolpion’, could be worn as a pectoral cross, and was an attribute of bishops during the Middle Ages. Over the course of the centuries, many of these crosses were produced in such a way as to hold a secondary relic. They might contain, for example, part of a saint’s clothing, pieces of the True Cross, or hair fragments. The cross was the most popular Christian symbol in Byzantium: it offered protection to the wearer and would have been available all over the Empire.
To disocver more about Byzantine art, please visit our relevant blog post: The Byzantine Empire, Art and Christianity.