The Oker comes out of the high Harz in a hurry, and the road through its valley follows the river's rush from the dam above down to the plain at Goslar. The valley is narrow, steep and wooded, with granite crags poking through the spruce above the road, and for a few kilometres it feels like a small Alpine gorge dropped into northern Germany. It is one of the best known bike roads in the Harz, and on a fine weekend you will see that the riders know it.
The bends are the point. The road follows the river in a long series of tight curves, some of them blind, with the water on one side and rock on the other, and the gradient is gentle but constant. The surface is mostly good, though the shaded sections hold damp and can have gravel washed down from the slopes after rain. A speed limit and enforcement are not unknown here, and the road has seen its share of accidents, so a measured pace pays off. Because the valley is narrow, the road is not wide, and you will meet coaches, cyclists and walkers at some of the pull-offs.
Geology is the story. The granite of the Brocken massif, a large mass of molten rock that cooled underground some three hundred million years ago, has been exposed by the river and carved into crags and boulders. A reservoir, built in the 1950s, fills the upper valley with dark green water and holds back the floods that once raced down the Oker, and there is a waterfall at Romkerhall, said to be the highest in the Harz, which drops in a long, thin stream over a rock lip. The spruce forest here has suffered from bark beetle in recent years, and the bare grey slopes are a reminder of how much the climate has shifted.
Services on the valley road are limited to a couple of small inns and kiosks near the reservoir and the waterfall. Goslar, about six kilometres away, is the nearest larger town, with fuel stations, supermarkets and a fine old centre that is a UNESCO World Heritage site. Altenau and Bad Harzburg are close too. Fill up before the valley, and bring a warm layer. Early on a weekday, when the mist lingers in the trees, it is a very good road.