The undisputed "best" part of the Rhine for cruising is the Upper Middle Rhine Valley, specifically the 65-kilometer stretch between Bingen and Koblenz in Germany. This area is a designated UNESCO World Heritage site known as the "Romantic Rhine." It features the highest density of medieval castles in the world, with over 40 fortresses perched on the hillsides, including the famous Marksburg and Rheinfels. This is also where you will find the legendary Lorelei Rock, a narrow and treacherous point in the river steeped in folklore. As you sail through this gorge, the landscape is dominated by steep, terraced vineyards that produce the region's famous Riesling wines. Most river cruise itineraries (like those from Viking or AmaWaterways) make this the centerpiece of their journey. While the entire river from the Swiss Alps to the North Sea is scenic, the Bingen-to-Koblenz stretch offers the concentrated "fairytale" imagery of castles, half-timbered villages, and dramatic cliffs that most travelers imagine when booking a Rhine cruise.