Cycling near Hannover I am looking for some routes for a road bike, about 150km - 200km, from Hannover with a come back by train. I will be going to Hannover in about a month for a week, and I'd like to see something. Do you know such routes?

I've been thinking about going from Hamburg to Hannover, and from Magdeburg to Hannover, these routes are about 150km each in straight line, but still, I don't know what exact route would be best here.

I've been also thinking about the route in the Ruhr Valley, it's about 220km, and there are maps on the internet.

Any recommendations?
One fun area is the Harz mountains. The ride to Goslar is around 80 km, and the old town is a sight as itself. From Goslar you can climb to the mountains and finish the trip at one of the several railway stops around the Harz area.