Aachen
Aachen has a fascinating history as the seat of Charlemagne's Holy Roman Empire turned industrial city and spa town that's within walking distance of Belgium and the Netherlands.
If you would like a guided tour, here is some information: https://www.aachen-tourismus.de/en/plan/guided-tours/
Station strolls
Station strolls
Here is an idea or two for a walk from the station
Around Aachen
Around Aachen
If you'd like to go further afield, here is a map with some walk and cycle rides.
...and here are a couple of things around Aachen that caught my eye.