There are 3 main baths in Pompeii, the Forum, Stabian and Central baths. The Stabian baths, at the junction of Pompeii’s 2 main streets was the largest of all 3. It was badly damaged at the time of the earthquake of AD 62. Only the women’s quarters were in use at the time of the eruption.
  The Heated bathrooms were in the east wing. The men’s baths were at the 
  south end of the wing and the women’s at the north end.
  Both the men’s and women’s quarters had three rooms. A hot room 
  (caldarium) next to the boiler room. A warm room (tepidarium) and a changing 
  room (apodyterium). The men’s quarters also included a small circular 
  room with a cold plunge bath (frgidarium). The women’s quarters had no 
  frigidarium but there was a cold bath in the change room.
  After removing their clothes in the changing room, the bathers could either 
  have a quick cold dip or go straight into the warm room. This room was heated 
  to a constant temperature. It served as an acclimatizing room allowing the body 
  to get used to the change of temperature between the changing room and the hot 
  bathroom. This was particularly important when leaving the hot room in winter.
  In the boiler room were three large tanks for cold, warm and hot water. There 
  was a furnace between the hot tank that also heated the warm tank next to it. 
  The cold tank was on a solid masonry base. The hot air from the furnace passed 
  through holes at the bottom of the walls into the two hot bathrooms. Here it 
  circulated under the floor that was raised up on small rectangular pillars. 
  It also flowed up inside the walls and across the ceiling. After circulating 
  round the hot rooms it passed through holes at the bottom of the walls to heat 
  the warm rooms in the same way. It then passed out through small holes in the 
  end walls of the warm room: there are 2 of these exhaust holes in the west wall 
  of the women’s tepidarium and four in the east wall of the men’s. 
  Behind the bath in the men’s tepidarium is a small fireplace. This was 
  a draught fire that was used to draw through the hot air.
  The women’s quarters were reached by two corridors, one from the west 
  and one from the east side. These two corridors led only to the changing room. 
  It was impossible to get from these corridors to any other part of the building.
  Originally, the women’s quarters were entirely isolated from the rest 
  of the complex. Later a doorway was put in only after the earthquake when the 
  men’s baths were out of action. Alternatively it might have been a service 
  entrance, which was kept locked during working hours.
  In contrast to the ruined state of the men’s baths, the women’s 
  baths are in excellent condition. The changing room still had its roof intact 
  when it was excavated. Although the roof of the hot room had collapsed, most 
  of the room is in a good state. The nipple tiles are still on the walls and 
  most of the decoration, including apart of the ceiling has survived.
  At the east end of the women’s hot room is a bath (alveus) made of masonry 
  faced with marble. Not only is the bath itself intact, but so is the system 
  for keeping the water ho. At the right end of the bath there is a semi-circular 
  opening. Inside this is a half cylinder made of bronze. This container sits 
  immediately above the Hypocaust channel leading from the furnace. It is set 
  slightly lower than the bath. As the water in the bath coos, it sinks and so 
  ends up in half the cylinder where it reheats and rises, thus keeping a permanent 
  circulation of hot water in the bath. A similar system operated in the men’s 
  hot room, but today it is completely in ruins.
  The baths held about 8 people. These who wish to bathe on their own could use 
  individual bronze tubs. The remains of one of these was found in this room. 
  At the other end of the room was a labrum, a shallow wash basin made of white 
  marble.
  Normally bathers would be rubbed with ointments in the warm room before entering 
  the hot room. Here they would sweat in the intense heat. The room was so hot 
  they had to wear special clogs to protect their feet from the hot floor. After 
  sweating they would take a hot bath followed by a cold plunge and then return 
  to the hot room for a second sweat. Before leaving the heated rooms they would 
  be rubbed down again with ointments as a protection against the cold.
  Public toilets are found wherever people gathered, such as the Forum, theatre 
  and the baths. The example in the Stabian bath is a typical Roman latrine. Along 
  three sides of the room is a deep trough. This sloped downwards so that water 
  entering at the higher end flowed out at the lower. Above this were seats supported 
  by blocks of stone set into the wall. No remains of the wooden seats were found. 
  However, store seats have been found at several sites. These have small holes 
  in the top, which are extended to form a U shaped hole along the front. About 
  30cm in the front of the seats is as shallow channel, also with the flowing 
  water. The people cleansed themselves with a sponge on the end of a stick, which 
  they used through the U shaped hole and then rinsed it in the shallow channel.
contributed by Belinda
Pompeii: Daily life, Bodies of Evidence, The Stabian Baths Glossary