The city is part of the Rhein Metro area comprising 5.8 million people.
II: The Popes During the Carolingian Empire, 795–858" (1906)* DeCormenin, Louis Marie; Gihon, James L., "A Complete History of the Popes of Rome, from Saint Peter, the First Bishop to Pius the Ninth" (1857)== Zunanje povezave ==*History of the Popes, The lives of the Popes in the ninth century: Gergory IV, A.D. 827-844.