But on to Aachen, which at one point was the effectively capital of the (Western) world, where Charlemagne settled and ran the Frankish Empire, as he was fond of the thermal waters here.
The thermal spring is still here, at Elisebrunnen, and sulfurous water still emerges at an even 53°C, which you can drink if you want to… it has a vaguely eggy taste.
These days the spring has been covered by a monumental building, which has ornamental taps that allow the spring to pour out into the drainage system, and it’s free for anyone to drink from.
Spa towns like this are all over Europe, but this is one of the best known. For centuries spa towns were places where the (mostly rich) people came to heal, as the waters were considered to have healing properties. Most of the actual healing came from being pampered and relaxing, and being fed and cleaned regularly, and the contemporary equivalent of doctors and nurses would gravitate towards these spots.