Round town in Germany

Here:

The Bavarian city of Nördlingen is maybe the only town in the world built using materials of extraterrestrial origin.

Maybe, maybe. What I like about the Bavarian city of Nördlingen is that it’s round:

Note Nördlingen’s very thin and very sensible Green Belt, a circular park with lots of trees, by the look of it. Unlike London’s Green Belt, which is absurdly thick and ridiculous, and, to an appalling degree, treeless.