Münster is a beautiful city and definitely worth seeing. It has a very nice city museum and a Picasso Museum, a lake, a star-formed botanic garden behind the castle and much more. I was there for a day this October and enjoyed it very much! Like in Aachen there are bikes everywhere but Müster also got a street just for bikes!

 

for more infos – check here:
http://www.muenster.de/stadt/tourismus/en/index.html

Picasso Museum:
http://www.kunstmuseum-picasso-muenster.de/index.php?id=46&L=1

for the NRW ticket – check here
Free trains in NRW