After immersing myself quite deeply in the topic of bathing, I thought I should share some particularly noteworthy places that take the experience of sitting in pools of water to a new level. And one of the most memorable baths is the Polynesian Spa in the town of Rotorua in New Zealand. BTW, 
On Top of a Supervolcano
The one thing that makes Rotorua a perfect spot for natural hot springs is the volcanic activity under the ground surface. In fact, it's more than one would expect from such a chilled location. Much more! Under the center of New Zealand's North Island lies a massive supervolcano, the kind you may be familiar with in Yellowstone. They are so powerful in nature that an eruption would instantly make all the carbon footprint of human history seem insignificant, and life as we know it would vanish from the earth for enough time to let something else evolve. A tiny taste of the possible destruction was offered on White Island, an outlier of the same volcanic complex, in 2019.
But until such a doomsday eruption, we may as well enjoy the naturally heated waters rich with sulfur, which gives the entire area of Rotorua a distinct smell, as the water bubbles up in steamy pools from underground. In fact, the same town is also known for its geysers, which native peoples have used for cooking. Also quite ideally, the same area has also a number of freshwater lakes, offering a nice contrast of cold waters without all the sulfur. The conditions could not be any more ideal for a bath, so the location of the Polynesian Spa is not the least coincidental.
Pools of Various Temperatures
True to its name, the spa offers different ways to enjoy the waters, whether you prefer your quiet privacy, or rather enjoy the bustle of many people. Over the years I have visited the place twice, and checked out both sections. In either case you get to sit in the rich thermal waters, while looking out at Lake Rotorua. Though the lake is close enough to reach out and touch it, the rich aquatic life in it (particularly the birds) make it much nicer to look at rather than be part of it.
This does not mean that there is no way to practice the hot-cold change I've discussed in my first Art of Bathing post. The temperature of the pools ranges from body temperature up to 41°C (106°F), plus there is an tiny but deep pool of ice cold water to take a plunge... and then get out to enjoy the warm air, even on a cold day. Yes, that's the great thing about heating and cooling your body. If there was any snow (not too likely on the North Island), you could probably roll around in it.
Healthy Minerals
Of course, a self respecting spa wouldn't base its healthiness on the temperatures of its water alone. It's all about the healthy minerals, after all. One of my favorite pools at the Polynesian Spa is the Priest and Radium Spring, which is rich with sulfur and silica, and also has a low pH level. This water has a reputation for being particularly sought after by sufferers of rheumatism, and general pains of joints and tissues. Though I cannot attest to any of this, sitting in this water did feel nice on my skin. Maybe it was the water's acidity?
Otherwise what I really liked about this spa was is relaxed nature, precisely for being so close to nature. All around the pools there was a pretty garden, complete with waterfalls trickling down the mossy rocks. There are also rest areas, where you can dry off and relax on reclining benches in between the hot-cold sessions. All in all a lovely experience I can highly recommend.