Aachen was lovely, clean, and full of good shops, great historical significance, and really nice people.
You can see everything in the city in 1 or 2 days. The main attractions are the famous cathedral and nearby Rathaus/museum.
For spa-goes, the Carolus Thermen are a must.
Aachen is a lovely town with a good historical center. Not too big, because of the wars I guess, but very impressive.
It's a spa-city with hot springs. I also found a good Thai massage center and the massage was very good (I live in Asia and can tell a good massage from a bad one). What I liked most of this city is the kindness of the people. It must be because the city is small and rich. It makes people very relaxed and, therefore, nice. The location is also nice since the borders with Belgium and The Netherlands are very close and one can always take an excursion. Nice place to spend a few days. Remember to take a sweater. Although I was there in June, it chills out in the evening. Not like it's cold, but you's better wear something more than a t-shirt.