Cologne becomes a modern metropolis. The new volume of the successful history of the city of Cologne focuses on the 19th century, which transformed Cologne into a modern city. Historian Jürgen Herres vividly describes how Cologne developed into the economic and transportation hub of the Rhineland. The period from 1815 to 1871 was particularly a time of founding for Cologne: in 1842, the city, the Catholic Church, and the Prussian monarchy decided to complete the Cologne Cathedral. The Rhineland Carnival took on its present form during this time. Renowned pioneers and entrepreneurs, such as Sister Maria Clementine Martin, inventor Nicolaus August Otto, banker Abraham Oppenheim, art collector Sulpiz Boisserée, clergyman Adolph Kolping, and even Karl Marx, shaped the city, its society, and its future.