The Upper Middle Rhine Valley is an outstanding example of a European cultural landscape. The World Heritage Site comprises the 65 km long section between Koblenz and Bingen / Rüdesheim and the surrounding hills of the „Rheinisches Schiefergebirge“ (Rhenish Slate Mountains). The unique appearance of the landscape resulted from both, the natural course of the river and the human activities. During the last two millenniums, this section of the river was an important trade route, a border, the place of exchange between cultures, and battlefield in several wars.
Undoubtedly, a boat cruise is the best way to visit the Upper Middle Rhine Valley. On a hot summer day in August 2012 we started at 9 am in Rüdesheim with the first boat tour. The trip to Koblenz takes four hours, the return by train takes one hour. The boat ride is also available in the reverse direction, but upriver it takes two hours more. Sitting on the upper deck, we enjoyed the view to the steep vineyards, the castles, and the picturesque villages that lie on the narrow strip of the shore. Almost on every hill and cliff, there is a castle or ruin. We have not counted them, but according to our guide book, there are more than 40 of them.
The castles were built between the 12th and 14th Century, but most of them were destroyed in the following centuries, during the Thirty Years' War and the War of the Palatine Succession. Many castles were rebuilt in the 19th Century, in the period of the Rhine romanticism. Many are privately owned, but some can be visited. The most rewarding are the Marksburg (the only medieval castle at the Middle Rhine that was never destroyed), Stolzenfels Castle (in neo-Gothic style, a good example for the Rhine romanticism), and Pfalzgrafenstein (a former toll station on a small island in the Rhine, it can be reached by a small ferry from Kaub). However, I have visited these castles many years ago during a bike trip along the Rhine valley and I have only vague memories of the interiors. At that trip we stayed overnight in the Stahleck Castle in Bacharach and I can confirm the review of Ian Cade, that it's a fantastic place for accommodation.
If possible, you should make also a detour uphill to some of the numerous viewing points. There are several places where you can enjoy a beautiful view of the Rhine Valley. I can recommend the following: the „Rheinblick“ in Patersberg (photo, view to the famous Loreley, the Castle Katz and St Goar), the Stahleck Castle in Bacharach (the most beautiful town in the valley), the restaurant „Gedeonseck“ near Filsen (view to the Boppard Loop where the Rhine makes an impressive curve).
If you are travelling by car, you should note that there is no bridge over the Rhine between Mainz and Koblenz. But you can cross the river by one of the ferries.