Mittelrhein, one of the smallest wine regions in germany better known to the outside world for its cliffs and castles than its Rieslings, which however can be outstanding. Most of the 469 ha/1,158 acres of vines planted in 2013, 67% of them Riesling, grow within sight of the river rhine, often looking down upon it from a considerable height (see map under germany). The first commercial vineyards start just south of Bonn and none is found on the west bank of the river until Koblenz is reached, 58 km/36 miles upstream. Thereafter, they climb both sides of the Rhine gorge, wherever site, the mesoclimate, and much hard work make vine-growing a more or less viable exercise. The temperature is raised by the large volume of water in the Rhine (see topography), and in summer there is usually enough rain to maintain the health and strength of the vines on their porous, steep, heat-trapping slate and quartzite slopes.
