Twice I had an extra hour or so in Aachen and used the spare moments to tour the amazing cathedral.
I could have used more time.
This is the oldest cathedral in Europe and was built by Charlemagne for his coronation there in the year 800 AD. Numerous other Holy Roman Emperors as well as Germanic kings were also crowned here over the centuries, and it remains the final resting place of Charlemagne.
Aachen is practically on the border of Germany, where the Netherlands meets Belgium. If you're heading that way on a vacation, it's certainly worth a stop. Or, ifyou're into Gothic/Byzantine cathedrals, it's worth a journey all on its own.
The cathedral is in the heart of the old town which is quite attractive in it's own right, though of course rather touristy (it's been a pilgrimage site for over 1000 years!). Aaachen has a special treat called 'Printen' which are very similar to Lebkuchen. I buy a stack whenever I go through. I can highly recommend any of the Nobis Printen shops, though to be honest, it's rare to get bad baked goods anywhere in Germany.
Between the fresh Weissbier on tap, the backeries two to a corner in the old town centers, and the several thousand types of cheese and sausage on offer, I have a hard time not gaining weight on each trip.