Built around a rich thermal mineral deposit during the period of the 4^th– 6^th c. Diocletianopolis was not only a SPA centre but an important Christian city – a seat of a bishop. At that time a remarkable church building developed in the town. Diocletianopolis is one of the few Roman cities in Bulgaria where so many early Christian worship buildings were built. So far, 10 early Christian basilicas (churches) have been discovered and explored within and outside the city, of which only three are exposed and accessible at this stage.