DIOCLETIANOPOLIS (Mitko Madzharov – m_madjarov@abv.bg, Dimitrinka Tancheva) The explorations continued in the northwestern part of caldarium No. 1. The pool measured 12.10 m by 8.30 m and was 1.50 m deep. The western wall of the caldarium was discovered and it was the outer wall of the thermae. The northern wall of caldarium No. 1 was preserved up to 2.30 m in height. There was an arch built of bricks in the middle of the wall. Subsequently the space beneath the arch was walled. A second identical arch with space beneath that was subsequently walled, was documented to the east of the entrance on the northern wall. The marble plinths of the northern and western walls of the caldarium were discovered and a few marble tiles on the floor were preserved in situ. Caldarium No. 1 was 11.50 m wide, while the thermae were 30.85 m wide. The drain that took the water from the pools in caldarium No. 2 was explored. The drain was 1.10 m deep and paved with bricks. A Roman bronze coin and a few sherds of the 2nd – 3rd centuries AD were found in the drain. During the first construction period of the mid 2nd century AD the thermae also functioned as a nymphaeum.