In the first, socio-historical part of the study, the main periods of Prague's twentieth century history are described and explained, i.e. the period of Hapsburg monarchy, the period of the interwar Czechoslovak Republic, the Second World War years and Nazi occupation, the 41 years of the communist regime and the years after the collapse of communism in Eastern Europe. It was a century of unprecedented discontinuities and the city and its people went through seven different political and economic orders. This kind of history makes legitimate the following question: how were the city and its residents able to retain identity and stability. Different mechanisms were used, e.g. separating culture from politics, inventing civic identity, identity linked to the locality as well as to its history and to the local ways of life, and to stress monument protection. The study hints also at the risks of such defensive mechanisms. The last part tries to exploit the experience of Prague and similar cities for stimulating the interest in urban theory.