Charles I was a monarch of the Hapsburg line who was the last emperor of Austria and king of Hungary. He lost his throne at the end of World War I.

James I was a Spanish king best known for fighting the Moors during his reign from 1213-'76. He is also known as James I the Conqueror and James I of Aragon.

Richard I, better known as "Richard the Lionheart," served as king of England from 1189 to 1199.

Frederick I was the first king of Prussia. He ruled from 1701 to 1713 and helped establish Prussia’s cultural significance in Europe.

Leopold I was Holy Roman emperor during whose lengthy reign Austria emerged from a series of struggles to become a great European power.

Louis I succeeded his father, Charlemagne, as emperor, serving as ruler of the Franks for 26 years.

Charles I was a king of England, Scotland and Ireland, whose conflicts with parliament and his subjects led to civil war and his execution.

Constantine I was a Roman emperor who ruled early in the 4th century. He was the first Christian emperor and saw the empire begin to become a Christian state.

King Edward I reigned England from 1272 to 1307, during which time he conquered Wales, expelled the Jews and signed many parliamentary statutes.