The Romans used natural springs for bathing. Bathing was a collective endeavor and took place in public settings. In some countries, shared bathing became a symbol of social status. The sento of Japan, the saunas of Finland, and the Turkish baths in the Islamic world were all stomping grounds for VIPs.
The Romans brought the notion of public baths to the territories that they conquered. The Greeks did the same. The practice spread in the West during the 16th, 17th, and 18th centuries. The public bath became the foundation of the modern-day bathroom.
The bathroom may be considered a relatively new development. Personal hygiene was a low priority during the Victorian Era. People washed their hands and faces sometimes, but not the rest of their bodies. You may be wondering how nobody was bothered by the smell? Today, the body odors would seem repulsive, but in that era, everyone smelled the same.
Understanding of bacteria in the body came only in the 18th century. Bathrooms at that time were universally built outside because of the absence of plumbing. The advent of the Industrial Revolution made the sanitation situation even worse. With families packed cheek-to-jowl in small, terraced houses, hygiene suffered. It was only toward the end of the 19th century that the concept of indoor plumbing began to take root. The availability of running water made it possible, and the rise of a moneyed middle class gave the concept traction.
The 20th century saw an increased emphasis on personal hygiene, especially with the introduction of soap and detergents to kill bacteria and keep people clean. Washing facilities were installed inside, and indoor plumbing became a legal requirement before a house could be built. While some U.S. homes still lack indoor plumbing, most Americans enjoy, and often take for granted, the luxury of bathroom facilities inside their house.