i went there 4days, last year , but in winter , beautiful city.
Didn't seen any shows but here's some cool stuffs /places :
this restaurant is nice , Trilobit:
http://www.tripadvisor.in/Restaurant_Review-g274707-d1233955-Review...
You have to try pork knee if you eat meat. I tasted it in an other restaurant, a big and loud restaurant in the center, don't remember the name or adress.
The park with the giant metronome was beautiful with the snow but i guess it's the same in summer. Nice view of the town.
You have to see the changing of guards at noon in front of the castle, At noon there's the orchestra playing . The song reminds me the Star Wars theme !