Friends and I took a trip to Mannheim for the day in March. A trip to Mannheim means...that people are probably going shopping at Ikea, which is nearby. This was the case for us as well, but we thought we should take a peek at the city for a bit, too, since we were close. I've visited several times since then because I've met people from there and it's an interesting enough bigger city (at least compared to Kaiserslautern!) to go shopping or grab a tasty meal.
During our first trip we visited the Schloss Mannheim (http://www.schloss-mannheim.de/en/). It was heavily damaged during the war so much of it was rebuilt and part of it also houses the University of Mannheim. We grabbed some excruciating audioguides in English and managed to listen to an hour of them. There was some good information in them, but they were so long-winded that it took 10 minutes just to get through one room.
While we were listening intently to the first 10 minutes of audio, we notices many police vans pull up in front of the castle and out spilled cops who started donning what looked like riot gear. At that point, we were all confused. No one was around except for the cops.
At the end of the tour (or, more aptly, after we had enough of listening to the audioguides), we asked the museum staff while all the police were there. They told us that there was a football (soccer) game later on that day and they were there for that, if need be.