Nördlingen is one of the most distinctive stops on the Romantic Road. The old town sits inside a complete medieval wall, but its real oddity is geological: the whole place lies in the Nördlinger Ries, a 25 km-wide meteor impact crater formed about 15 million years ago.
That circular setting gives the town its shape. Streets radiate from the market square to the gates, and from the tower of St George's Church you can see the crater rim forming a low horizon around the town. Many older buildings were made with local suevite stone, a rock created by the impact and famous for containing tiny diamonds.
Nördlingen is quieter than Rothenburg ob der Tauber, which is part of the appeal. You can walk the wall circuit, climb the Daniel tower, and still have the lanes largely to yourself outside the busiest summer weekends.