The Holy Roman Empire, also known after 1512 as the Holy Roman Empire of the German Nation, was a political entity in Western, Central and Southern Europe that developed during the Early Middle Ages and continued until its dissolution in 1806 during the Napoleonic Wars.
The latter territories lay within the Holy Roman Empire and its borders, but were formally divided between fiefs of the German kingdom and French fiefs such as Charles's birthplace of Flanders, a last remnant of what had been a powerful player in the Hundred Years' War.
The Holy Roman Empire, 1495-1806: A European Perspective. Brill. ISBN 978-90-04-20683-0. Bryce, Viscount James Bryce (2019) . The Holy Roman Empire. Good Press. ASIN B081TFMGRC. Chaloupek, Günther (2015). "The Congress of Vienna and the Emerging Rivalry between Austria and Prussia for Hegemony in Central Europe".
A German Confederation of 39 states, under the presidency of the Austrian Emperor, formed from the previous 300 states of the Holy Roman Empire. Only portions of the territories of Austria and Prussia were included in the Confederation (roughly the same portions that had been within the Holy Roman Empire). 
Vienna (/ v i ˈ ɛ n ə / vee-EN-ə; German: Wien (); Austro-Bavarian: Wean) is the capital, largest city, and one of nine states of Austria.Vienna is Austria's most populous city and its primate city, with about two million inhabitants (2.9 million within the metropolitan area, nearly one third of the country's population), and its cultural, economic, and political center.
The Byzantine Empire, also referred to as the Eastern Roman Empire or Byzantium, was the continuation of the Roman Empire in its eastern provinces during Late Antiquity and the Middle Ages, when its capital city was Constantinople.
The Catholic Church, also known as the Roman Catholic Church, is the largest Christian church, with 1.3 billion baptized Catholics worldwide as of 2019. As the world's oldest and largest continuously functioning international institution, it has played a prominent role in the history and development of Western civilization.