Sentō
People built the first sentō during the Nara period, in the 700s.  The first people to use sentō were monks.  They used the sentō  for ritual purification. Later, more sentō were built for ordinary people to go and get clean.  By 1700, most of the neighborhoods in Tokyo, then called Edo, had their own bathhouse.  Many of the sentō of that time were steam baths, not soaking baths.  They did not have windows, so the bathers could not see very well.  Sometimes the water was dark and dirty.