The B4 is one extraordinary piece of road. If you like high-speed sweepers that is...
The B4 literally is the extension of the Autobahn A395 coming into Harz from the North (Braunschweig). It is by far the quickest way to enter the Harz area. As the B4 hits the foot of the Harz Gebirge the road starts climbing the mountains in perfectly swept, very broad and attractive turns worming its way uphill at a quite steep incline.
The lay-out of the road calls out for some relatively high-speed action but be very careful the first couple of kms as there are still fairly many houses along the road up from Bad Harzburg.
When you reach the top at Torfhaus (approx half-way between Bad Harzburg and Braunlage) make sure to make a stop at the parking-lot & restaurant Brockenblick to take a couple of photos of Harz highest mountain Brocken (1141m) and maybe chat a bit with some of the many other bikers there.
Ride carefully - but have fun...! :o)