Late Antiquity feels right, but I dabble so extensively that there is no best fit.
My political setting centers on several large Roman states that continue to manipulate their barbarian neighbors. Imagine Second Century Rome stretching its influence into North Central Europe as late as 1066 AD.
Scientific development, education, and commerce are roughly comparable to the late 1200's. Instruction is a unified curriculum of natural history and theology, with each major city having a university. A spirited rivalry exits between Aristotelian and Platonic schools of philosophy.
If I strickly limited myself to one era, I couldn't play with anachronisms. For example, I enhance the ancient tradition of long book titles, as in "Saint Lansadore's Exhaustive Study of the New World's Coastline with Commentary on its Monstrous and Hostile Inhabitants."
An example of a modern anachronism is a nervous disorder known as "prolonged enchantment psychosis."