Water that supplied a large complex, such as the Baths of Caracalla, came by aqueduct from specially selected springs in the hills outside the city of Rome. Some of the water would run down slope along the hillsides, but aqueducts were needed to bridge the valleys and keep the water on a slight slope. Making water run down too steep a slope and then run up again on the other side created what is called a siphon and it caused too much pressure at the lower point of the curve, thus necessitating that the aqueduct keep the water slope gradual. The water traveled along a water channel that the upper part of the aqueduct, called the specus, S-P-E-C-U-S, and then it flowed down into a water distribution center, or castellum, C-A-S-T-E-L-L-U-M. The specus was lined with cocciopesto, C-O-C-C-I-O-P-E-S-T-O, or waterproof mortar. And it had little manholes at the top of it where the water police could jump down and investigate any problems. Water for emergencies while the aqueduct was being cleaned out, or if it were damaged and service interrupted, was stored in numerous cisterns at the edge of the Bath complex. The Baths of Caracalla were designed to serve people of what was roughly the middle class of free people in Rome, individuals not rich enough to have their own elaborate private baths in their homes. It was more like a mall than simply a bath. And people would go not just to get clean but to engage in political clubs, religious services, shopping of all sorts on several levels, paying their bills. Taking care of their obligations to the state, money lending. Oh a variety of services. If bathing was desired, it could also be a social experience where one would meet one's friends. Clothing was left in the apodyterion, that's A-P-O-D-Y-T-E-R-I-O-N, or the changing room, and placed in a locker. If the bath visitor was well enough off to have a slave or a client in his service, that individual might wait on the bench in the apodyterion for the individual to finish bathing. And he might keep watch on the clothing stored, or the bone ticket that had been offered to him as a clothing check. Once inside, the bather might opt for a wide variety of choices. Males and females might bathe at different hours in some bathing establishments, or in different areas at others. Occasionally they may have even bathed together, for there were ordinances against that. Often a bath complex would feature a large natatio, N-A-T-A-T-I-O, or swimming pool area, such as the one In the Baths of Caracalla. Behind the pool was a huge triple grind vaulted space which had unheated water in pools at either end. It was called the frigidarium, F-R-I-G-I-D-A-R-I-U-M. But it was really a huge space where beautiful art was displayed, where one could stroll around and meet one's friends and one could prepare to go to the small room beyond known as the tepidarium, T-E-P-I-D-A-R-I-U-M. Now the tepidarium was a transitional space which lead to the rounded caldarium, C-A-L-D-A-R-I-U-M, which was a hot room where one could experience temperatures well over a hundred degrees, and which provided the sort of contrast to the colder frigidarium that many Romans admired. Besides the caldarium there were extreme high temperature rooms or sudatoria, S-U-D-A-T-O-R-I-A. As well as rooms for massages and a large exercise area known as the palaestra, P-A-L-A-E-S-T-R-A. Most large baths even had bowling alleys, where the game of nine pins might be played. The caldarium consisted of an upper level floor which was supported by small columns which were just a few feet in height and usually made of brick. These suspender bricks, or suspensurae as they were called, S-U-S-P-E-N-S-U-R-A-E, rested on a lower level floor. The bricks allowed hot air to circulate around the space between the upper and lower floors, and to provide heat for the caldarium. The excess heat would be driven up flues in the walls, and carried out of the building. The heated walls, and floor thus accounted for the elevated temperature of the caldarium. But an oven, or what was known as a praefurnium, P-R-A-E-F-U-R-N-I-U-M, had to be situated close by in a little courtyard and continually stoked with wood by the slaves or the attendants running the complex. This is known as the hypocaust heating system of the Roman baths. The hot air came into the complex from the praefurnium and it circulated. It could even go under the emersion pools within the caldarium. Something called a testudo, T-E-S-T-U-D-O, or a bronze container in the form of a tortoise shell, could be placed inside the pools and would constantly be heated from below, enhancing the circulation of hot water throughout the pool. Thus, creating a jacuzzi-like effect for the bather situated near it. The Roman bath complexes, a fusion of the Greek palestra idea and the Roman desire to create world making spaces really caught on. And by the first century CE, every community insisted on having a bath. People even had them in their homes, if they could afford them. And even private clubs could have their own bathing establishments as a lure to attract and delight members. It was also a way to keep the masses of Roman people happy through a social outlet that made everyone feel as if he were a king or a queen, if only for a little while. >> Now if you can picture this I am actually walking on the basement level below the caldarium. Now over here in this area would have been the furnace, and the heat, the hot air generated by that furnace would've followed along these channels created by these brick pillars all throughout the basement. All the way, and look over here. The heat then would've travelled up, up, up, to the floor of the caldarium. This is where the bathers would have been standing and this is how the caldarium itself was heated. It's the forerunner of today's central heating system. [MUSIC] They were pretty good at regulating the temperature of the caldarium, but even so Roman bathers usually use these wooden sandals in order to keep their feet from being scorched on the hot floor. All in all, looking at how these bathing complexes were designed and constructed, I'm thinking the ancient Romans must of had a very basic understanding of thermodynamics, at least that hot air rises. Look at these walls, they seem solid, right? Wrong. Because look at a section of the wall turned on its side. The bricks are hollow so that the heat from the furnace was able to travel up through the walls, making the caldarium all the hotter. No one knows for sure, but I'm told that the temperature of the caldarium could have reached upwards of 100 degrees Fahrenheit or more. Basically, it's the historical roots of today's sauna. >> Of course, people had to use restrooms, too, but they were more public about it than we are. And of course, they didn't have toilet paper. >> This is one of the main latrines here in Ostia and as you can see it's pretty roomy. It could accommodate up to 25 people. And this is my good buddy, Anthony Tuck. He's an archaeologist out of Tufts University in Boston. So Tony, my understanding was that this was a public toilet, right? >> Yes it was. For a small fee both men and women would use this space. They would come over here and do their business. >> Men and women? There was no division of the sexes? >> That's true. As you can see there's not any division between each individual space. It was a very communal environment. People would chat and talk very much like we're speaking right now. >> So it was like a social hangout? >> It certainly was. >> You could conduct a business deal? >> Yes you could, you could. You could hangout here waiting for a dinner invitation. >> So when everybody was done with their business, I mean. >> Was there anything like toilet tissue, toilet paper? >> No, paper in the ancient world was very expensive and very scarce. And as a result, normally what they would do is they would simply have a sponge on a stick. Something kind of akin to this. >> [LAUGH] You gotta be kidding. >> When someone was finished they would clean it off. It was their responsibility to clean it out and leave it for the next person. >> So everyone shared this thing? >> Everyone shared it. The Romans didn't have a sense of hygiene, of bacteria. That's obviously a 19th century concept. >> Of course, yes. That's right, Louis Pasteur. >> And so, as a result, this is how they managed. >> That was it. Unbelievable.