DIOCLETIANOPOLIS (Mitko Madzharov – m_madjarov@abv.bg, Dimitrinka Tancheva) Room No. 04 was thoroughly explored, situated to the west of Rooms Nos. 1 and 2, which were caldarium and tepidarium. A second northern pool, 7.55 m wide, was explored. Bricks, fragments of mortar and pieces of the vaulted ceiling were found. Both pools in the room were separated by a wall of bricks faced with marble veneer. The newly discovered pool was situated at c. 15 m from the catch, which provided hot mineral water for the eastern part of the thermae. The northern wall of Room No. 04 was built in opus mixtum and was preserved up to 1.50 m in height. An entrance, 1.50 m wide, was documented. Sectors from the marble plinth, which separated the northern wall from the path, were discovered. Room No. 04 was a caldarium. The finds included Late Antique sherds. A layer with traces from fire was documented close to the northern wall.