File:Sagalassos Imperial Baths in 2012 2733.jpg

English: Translation: The 'Imperial' Baths (from approx. 120 to approx. 590 AD)

When Hadrian (AD 117-138) chose Sagalassos as 'neokoros’ or official site for the imperial cult in the province of Pisidie, the Lesser Baths proved too small for all the Pisidians who took part in the Imperial festivals and games. The hill on which the [earlier] Small Baths were built was extended into a concrete and brick building terrace of more than 5000 m2. The 2 m thick outer walls consisted of smooth limestone blocks with a concrete cladding on the inside. Surrounding a central Marble Hall' or 'Emperor's Hall' were two L-shaped bath complexes consisting of a caldarium, tepidarium and frigidarium: a smaller one along the entire west and part of the north wall, a larger one along the entire south and east wall. The entire length of the latter ran a continuous space with a central frigidarium (with a western bay window with a sitting bath) between two elongated apodyteria (with niches for storing clothes). This element was borrowed from contemporaneous bath complexes in Ephesos, the largest center of Anatolia. The same applies to the richly decorated vestibule or basilica thermarum, which provided access from the north to the 'Marble Hall' with its statues of emperors, gods, city founders and aristocrats. At the end of the 4th century AD. the building was thoroughly reorganized. The 'Marble Hall', which, according to an inscription in 165 AD. was dedicated to the emperors Marcus Aurelius and Lucius Verus, became a third caldarium. The colossal statues of Hadrian and Marcus Aurelius and their wives, as well as those of Faustina Maior and her husband Antoninus Pius, were placed in the niches of the southern apodyterium. There they formed a decorative background for the central hall of the large frigidarium that now functioned as a banquet hall. The basilica thermarum was fitted with a plunge pool and replaced accordingly the old frigidarium.

After an earthquake in ca. 500 AD. the caldarium-tepidarium complex on the south side became a boiler room caldarium and the elongated space in the east was given a new mosaic floor. Around 590 AD. the bath complex was largely destroyed by a stronger earthquake, although certain halls were still used for banquets afterwards.