In 1802, the Viktor-convent was secularized by Napoléon Bonaparte, and the libraries of closed monasteries and the convent library were merged. After that, the economic situation deteriorated more rapidly. A town gate called the "Marstor" was torn down in 1821, and the "Scharntor" and parts of the town walls were removed in 1825. The removal of the "Klever Tor" and a mill called "Kriemhildmühle" was prevented by a town councillor in 1843. At the same time, the ruins of the "Colonia Ulpia Traiana", which had been used as a quarry since the Roman settlement was given up, aroused the interest of archaeologists.