This is a large complex on three levels. Its opus sectile floors and walls, the use of suspensurae to heat the spacious rooms on the top floor (14-19), the presence of one-person latrines (20, 21), easy communication with the Heliocaminus Baths and the Stadium Garden, as well as its location near the Imperial palace all suggest that the building was used as the emperor's residence during cold weather (hence the name "Winter Palace" sometimes given to it). Room 16 could hold a large number of people for receptions or meals. Room 18 has been interpreted as the emperor's bedroom. If Adembri and Cinque are correct, rooms 14-19 may also have been cooled by an exhaust furnace in hot weather (B. Adembri, G. Cinque, "Edifico con peschiera," Lazio e Sabina 6 [2010] 52-53). Other reception rooms were located in the center of the lowest level off the Stadium Garden. The quadrangle (2) around a large pool (length: 28 m) decorated with statues in the 24 niches attests that the building was used in the warm months both for bathing and, below in the cool cryptoporticus, for walks. The pool was surrounded by a colonnade composed of forty fluted white marble columns in the composite order. The structure dates to Phase II (125-133 CE).