|Indoor plumbing is an amazing (and much appreciated) invention. Imagine living all those centuries with freezing dirt, tile or mosaic floors. Forsooth, cold tootsies would be the order of the day.
When someone says indoor plumbing, they almost always mean the toilet. But plumbing per se, also meant pipes that carried water, and hence the method of filling bath tubs.
History makes note of a wide variety of indoor conveniences, although few of them boasted the amenities we have today. In Babylon for instance, King Sargon the Great enjoyed a really big bath room, literally and figuratively. It was a room with the floor and lower half of the walls lined with baked bricks, and a slope in the floor leading to a drain. Water was just poured over the bather and drained away. There are reports that he also had indoor seats used as toilets, with drains leading to the sewer and thence the river. Remains of the drains and piping have been found, but the conveniences conveniently vanished. Still, not bad for the 7th century B.C.