Zurich, member of the Holy Empire
The sophisticated town built by the Romans deteriorated after their departure in the year 401. The Francs and the Alamans who followed did not have the necessary knowledge to maintain the Roman infrastructures. These deteriorations lead to the destruction of the navigation system, and to the stopping of the commercial practices of the town. Several kings and emperors exerted their power over the In Lindenhof and the Roman fortress was transformed into a castle. In 1218, Zurich became an imperial city and was placed under the direct authority of the Holy Roman Empire. Around the year 1300, the first walls of the city were built, as well as monasteries and convents which also acted as surrounding walls. According to legend, Charlemagne was supposed to have built the church of Grossmünster on the site of the tombs of the Patron Saints of the city, the martyrs Felix and Regula.