Baths of Antoninus. Emperor Antoninus was better known as Caracalla, and so his baths are known more commonly by that name. The ruins of the baths are well preserved with many of the mosaics in tact. Building began in around 212 AD. The baths had 4 levels, 2 above ground and 2 below. There were cold. tepid, hot, steam, and open air baths available and the baths could accommodate 1600 people at one time in the various baths.