A sento is a Japanese communal bath house. These bath houses are quite utilitarian, with one large room separating the different sexes by a tall barrier, a line of showers alone a wall and a single large bath tub for the bathers to sit inside together.
Bathers are supposed to wash themselves up along the line of showers then step into the bath tub. No soap should ever enter the bath tub and all bathers are supposed to go inside naked without any under garments or swim suits.
A special form of the sento is an Onsen, which is a sento using water from a natural hot spring.
Public baths (public in that anyone may use them as opposed to the private baths of ryokan and hotels which may only be open to guests)can be found throughout Japan and typically cost 200 to 2000 yen.