The route from Passau, on Germany's eastern border, to Vienna is one of the most popular cycle paths in Europe, and it's no wonder! This stretch of the Danube carves its way through a thousand years of history; 60 dramatic castles and palaces lie along the river and the ever-changing landscape is a kaleidoscope of fertile plains, narrow gorges, lowland forests, bird-rich marshland and acres of picturesque vines.