Day 24 - With an early start to a warm and sunny day we decided, rather than battle the Paris tube at peak hour, that a cab to the station was a better option. We hopped on the TGV (don't know what it means) for a very fast trip to Mannheim. The monitor in our carriage showed a top speed of 321kph, and a cruising speed around 280kph. The brochure told us that this train holds a world speed record of 574.8kph which it set on 3/4/2007. The ride today was so smooth it didn't feel that fast but when a train from the opposite direction went passed, it was all over in about 2 seconds. At Mannheim it was a change for a much slower 12 minute ride into Heidelberg. We checked into the Marriott located right on the banks of the Neckar River which flows through the town. Early afternoon we decide on a walk up through the old part of Heidelberg, an area full of eateries and small shops. At the far end of the town we hopped on a cable car which took us on a short ride up to Schloss castle, with great views over the city, river and mountains that were close to the opposite bank. The castle was not as spectacular as others we had seen so far as it was in a fair state of decay, so much was not accessible. It was back down town for a return walk along the river finishing with a 50 minute cruise. This gave the legs a rest for a while, taking in the buildings and parks that lined the river. The 200 passenger boat was totally electric, with motors driven off batteries charged by a huge array of solar panels that formed the roof. The cruise finished around 7pm so it was off to an historic local pub (called the Hip Hotel) for a taste of some local German food. A short tram ride got us back home for an early night.