Most of the pictures here are of the castle which is on the hill overlooking the town, it is marked on the map as Königstuhl, I believe.
Part of the castle was destroyed by Napoleon or something, but the city liked it that way and/or had not money at the time to repair it, because by that period cannons and population sizes had caused castles to be obsolete as defenses for a city. Today, according to our guide, it costs the city more to maintain it as a ruin than to restore it.
Here's an example though of how the ruins look:
On the far side of the palace which had been restored, their was a view of the city.
Afterwards we had "freetime" which is a funny word for it since we were all adults and could do whatever we wanted, keeping in mind that the boat would not wait for us. Mom and I ditched the tour early since it was raining and coffee sounded better. The weather cleared a little and we found this plaza where I barely captured two tourists taking a jumping picture, an Education Abroad Program (EAP) photo winning favorite genre of picture.
At this point you should be able to find the wikipedia article if you are interested, but to continue to facilitate it, I will include it as a link at the bottom of each article without any explanation:
