During the restructuring of the hotel complex of the southern building of the Koch hemicycle in the Piazza della Repubblica, ancient structures that have building phases preceding the construction of the Baths of Diocletian were revealed.
All of the structures discovered, reflecting the same alignment, confirm that they belonged to a single monumental complex, consisting of scenographic fountains and basins, adorned probably with sculpture immersed in a green space. The architecture, found over an area of around 700 square meters, is difficult to read because the walls were in part obliterated by the construction of the building which cut through the unity of the building. The foundation wall of the Koch building was also formed with numerous fragments of ancient marble, datable to the early Imperial period, and follows the semicircular arrangement of the exedra of the external enclosure of the complex of the Baths of Diocletian.
The garden with rich fountains and basins (which were connected to one another by a channel dressed in white marble, and arranged on such different levels as to allow plays of water) was delimited on the south-east side by an imposing wall in opera laterizia with plinths of travertine, placed at regular intervals, that supported columns. The water supply was through fistulae aquariae.
The paving of the fountains is in opus tessellatum of large polychrome marble tesserae. In the corner of one basin, covered by hydraulic mortar, there was a lead sieve for filtering the water. The sieve, of hemispherical form with small circular holes and a folded border (still functioning perfectly), could be raised from its position for cleaning.
The complex on the northwest side is delimited by a corridor with a barrel vault and walls frescoed with geometric motifs in yellow, white, green, blue and red. (Maria Nicoletta Pagliardi)