We should note that all of these places of thermal extremes (Finnish saunas, Japanese hot baths, American beaches and mountains) have their opposites close at hand. There are possibly two reasons for having the extremes right next to each other.
The first is physiological: the availability of extremes ensures that we can move from one to the other to maintain a thermal balance.
The second might be termed aesthetic: the experience of each extreme is made more acute by contrast to the other.
Works of art which have great life often have intense contrast within: rough/smooth, solid/void, loud/silent, empty/full. It is the difference between opposites which gives birth to something. Contrast is what often gives other principles their degree of life – the intensity of the boundary, the markedness of the alternating repetition.
Contrast strengthens centers by making each a deeper entity of itself, and thereby giving deeper meaning to both. It is, at its simplest, what allows us to differentiate. But meaningless contrast remains meaningless. It is only when centers are actively, mutually, and meaningfully composed that it acts to deepen the whole.
Perceptual: "They couldn't figure out what to do next", "they couldn't find the feature", "they didn't know they could click that button..." etc.
Domain-specific: "We need a way to jump back here because in their workflow this happens..."
In general, usability testing only catches type 1 perceptual problems. Because in those tests you take people out of the real world and assign them tasks. Usability testing doesn't catch domain-specific problems because they only come up in real life use.