The brochure on the nightstand explained that it is called a furo. Furo is the Japanese word for a single-person hot tub.
The term "low tech" doesn't begin to cover the simplicity and functionality of the design. No bubbles, no jets, no electricity, nothing to break, just deep hot water up to your neck. Asians have known for thousands of years the benefits of sitting alone immersed in hot water. And, as I have since learned, the favorite place for Japanese college students to study is in the furo.
Basically, it is just a plywood box with a cool Oriental name. At first glance it seems like you may have your knees in your mouth, but this is not the case, due to your natural buoyancy—you feel so good you just don't care. I'm tall for a short person, over 5' 10", and I fit very comfortably. You get the same benefits of a hot tub, but none of the contamination consequences, plus you get to be alone and not feel completely antisocial. Try to remember, did you ever take a tub all alone and not feel self-conscious and wasteful? I did it once and felt as if I were driving a Winnebago to the grocery store.