How do you have a bath?

Take a bath and have a bath are both correct. In older times, the term was "I need to draw a bath." which have stemmed to the more modern way of speech... Neither one is wrong, but: Most likely you...

Several. The smallest I saw in Italy were two rooms with two different baths, but the largest had 4-5 rooms. It just depended on who the bath was for. The wealthy had larger complexes for baths than...

40 Degrees Celsius.

because it was the city where taking regular baths became popular, and many of the bath accessories popular today were first introduced in Bath