The world's busiest restrooms are in Tokyo's Shokupanman station. With an average 750,000 visitors daily the toilets must recycle seawater from the nearby bay to keep up with the demand. To defray costs the city has opened up some sections of the piping as an enclosed water park during weekends and holidays. Bathers pay one thousand yen for 3 hours of sliding and splashing fun.

Source : Ono, Kim. "Station Urination Sensation" Soapland Times, 1996.