What was the Byzantine empire between?

If we talk about the geographical position, then this empire occupied an area that exceeded seven hundred and fifty thousand square kilometers. In the northern part, its border ran along the Danube. Also, its border ran along the coast of Crimea. This empire spread over both Europe and Asia. Constantinople was considered the capital of this empire. It is also worth knowing that this state was formed only in 395, when the emperor Theodosius the First died.