Over 1600 years ago, the Romans built one of the grandest and most impressive baths in the world: the Imperial Baths. People bathed naked (not always separately), could engage in sports, sit in cold and hot baths, swim, get a massage, have the body hair removed by tweezers or wax, and be cleaned with the help of scrapers, pumice stone, or fermented urine. They could relax, gamble, do business, go to the hairdresser’s, libraries, reciting rooms, or pubs. 

When you enter the Imperial Baths (Kaiserthermen, fee) you will first come to the hot water bath (large enough for present-day theater and opera performances complete with stage, orchestra, and 650 seats). The incoming cold water was heated in altogether six boiler rooms, four of which are visible in the 19m (62 ft) high ruins which later served as a part of the medieval city wall. The 40° C/104° F hot water was then conducted into the three semicircular pools for the bathers. A hollow-floor heating system heated the pool floors as well as the rectangular central part of the vaulted hall. You can descend from here into the underground service tunnels and then continue to the cold water bath. The sports grounds are located outside the enclosed facilities.