This place is old and so very castle-like. The day we were there, the transportation shuttle was not in operation so we had to hike to the castle. It was not too hard, but would be difficult for older folks or during hot weather. The view from the top was worth it!
There is a nice little cafe at the schloss where we had coffee and cake and sat back and did a little people watching.
While sightseeing in downtown Heidelberg, be sure to stop at some of the small family run bakeries and shops and also walk across the bridge and look back at the city.