How did bath houses become popular

Bathing and concepts of cleanliness are not universal across societies. Cleanliness, for some, meant multiple times during a day bathing, while for others it may simply have a religious or spiritual significance, even while little bathing took place on a day-to-day schedule. For most of human history, private bath facilities were a rare commodity. Thus, it is the history of bath houses that is associated with social concepts of cleanliness and this was spread by factors that included empires, new religious/spiritual ideas, and other cultural influence.

Early Bath Houses

Perhaps among the earliest societies with bath houses included Indus region societies in the 3rd millennium BCE, who built forms of bath houses and established rituals for bathing. In fact, one the earliest large bathing, and likely public, complexes is found in Mohenjo-daro, where the so-called "Great Bath" is often considered the earliest public bath with the main pool measuring 11.88 × 7.01. Later Indian works, such as the grihya sutras, discuss the importance of bathing and hygiene that emphasized bathing three times a day as a way to keep the body clean. It was also seen as a way to stay spiritually clean, demonstrating that religious concepts of cleanliness sometimes were associated with physical cleanliness.

Both ancient Mesopotamia and Egypt have evidence for bathing in private spaces, such as homes and palaces, but public bathhouses are largely absent. In second millennium BCE, Akrotiri in Santorini and Knossos in Crete show evidence there were bathing facilities, although these, similar to Mesopotamia and Egypt, may have been for more wealthier individuals or classes. In fact, daily washing in a bathroom may have meant you were wealthy enough to have these facilities in your own private space. In Greece from the first millennium BCE, bathing had a more public aspect, perhaps similar to ancient Indian/Indus cultures. As the Greeks emphasized sports that meant participants were generally naked, where our modern term gymnasium comes from, communal baths for the competitors were required. Even some of the earliest showers may have developed in baths used for athletes between 500-300 BCE.

Later Bath Houses

As aqueducts and water supply technologies, such as qanats became more elaborate, public baths developed in more places. The Romans were well known for create large and elaborate bath houses that sometimes took advantage of natural springs, including hot springs or geothermal springs, as well as supplying water to specific sites using water transport technologies. The Romans probably built the most elaborate bath houses, where bathing was seen as an important aspect of religious worship as well as cleanliness. Bathing was so important to the Romans that there were social expectations that all classes participate in bathing. This led to the practice of the Roman government often commissioning large public baths, which were found in most Roman towns and cities. Rome, itself, had 952 baths of varying size, with the largest public bath from the ancient world being the Baths of Diocletian built in 306. Sometimes baths were associated with temples and religious practice, such as the Roman Baths in modern Bath, UK, where the main temple was dedicated to Minerva/Sulis. With this emphasis, baths became not only public but also spaces used to socialize, from meeting potential business partners, to buy and sell products, but also demonstrate one's status in society. In other cases, baths were also sometimes associated with prostitution or just casual sex between different sexes.

Romans often built baths as one of the first things in a town they conquered or built. People would also exercise, often to help built a sweat so that it is easier to remove skin and dirt, while they would also be massaged. Oil treatments, often of varying quality, would be made available to people. There were also two main types of baths, one hot (calidarium) and the other cold (frigidarium). Effectively, Roman baths began to become similar to our concept of spas, where people go to receive massages, skin treatments, relax, and bathe. Roman baths have most likely shaped our concepts of spa treatments and other cultures' bath that followed in the Medieval period. Bath houses continue to spread in many regions, including in Central Asia and China, by at least 200 BC, began having public bath houses. The spread of public baths could have happened through travelers and merchants that began to connect Eurasia during the Old World. Probably by around 1 AD, bath houses could be found anywhere between Britain and Japan.