The new childrens' clinic at Heidelberg University Hospital. The University Hospital is the third-largest hospital complex in Germany these days - after downsizing significantly.
One of a couple dozen old "NATO ramps" across the Rhine. Built in the Cold War, they were intended to serve as easy ferry access points across the river once the bridges were all blown up. There's an identical structure on the opposite side of the river.
The "Heathen's Hole", a 183-feet deep hole in a mountain. Dug about 2400 years ago, no one knows why. The grate is to prevent people from climbing or falling in (duh).