From its Alpine sources, the Rhine flows between Switzerland and Lichtenstein and into Lake Constance. The High Rhine (Hochrhein) is the name given to the section between Lake Constance and Basel, which marks the boundary between Switzerland and Germany. In this area, the river flows through the Black Forest and Mainz. It is joined by many tributaries from the Alps productive of rapids, which made it difficult to navigate until early in the twentieth century, although its meanders were straightened in the early nineteenth century.
The Middle Rhine winds for ninety miles in a deep mountain gorge, bordered by vineyards, in one of the most picturesque areas of Europe. Below Bonn the Rhine valley opens into a broad plain, passing Cologne and Düsseldorf. The last section of the Rhine lies below Emmerich in the delta region of The Netherlands, where it breaks into several branches.
After the Thirty Years' War and under Louis XIV in the seventeenth century, France claimed Alsace and extended some of its territory to the Rhine. Under Napoleon, France claimed even more territory. Under the Treaty of Lunéville (1801), the Rhine marked most of France's eastern boundary, but Napoleon advanced further, claiming much of northwestern Germany (as far as the Elbe and Neisse rivers) in the Confederation of the Rhine. In subsequent battles France lost much of the territory it had acquired, but the Congress of Vienna (1815) left the Alsace to France, thus giving the country a border on the Rhine.
The picturesque beauty of the Rhine, including the many castles along its banks, has made it a favorite of poets and artists, and the setting for many fairytales: Byron, for instance, writes, "the castle crag of Dachenfels frowns o'er the wide and winding Rhine."
A ruined Frankenstein Castle stands along the Rhine near Darmstadt, but there is no evidence the Shelleys knew of it: see title page and note.