The Eastern Roman Empire, located in Eastern Europe, once included West Asia and North Africa. It is the oldest monarchy in ancient and medieval Europe. But during its development, there were 12 dynasties and 93 emperors.

You think China is perfunctory, but I don't think so. The length of a country is not important, but the continuation of civilization. Chinese civilization continues to this day, although 1 1 century, Constantinople, the Eastern Roman Empire, has been the center of the western civilized world. But today's Eastern Roman Empire has long been unrecognizable. In this sense, China is the longest.