The Institutional seats of the European Union are all in places associated with the memory of the Holy Roman Empire. Brussels was viewed by Charles V as "the center of his Empire". Strasbourg was one of the main Imperial Free Cities, and so was Frankfurt – the latter being also where Emperors were crowned from 1562 onwards, in the "Kaiserdom". As for Luxembourg, its name is associated with Luxemburg dynasty which provided several Emperors in the 14th and 15th centuries. The most prominent prize awarded for work done in the service of European unification is called the Charlemagne Prize. The comparison of the European Union with the Holy Roman Empire, in a negative or positive light, is a common trope of political commentary.