Nördlingen, Germany: a complete circle of medieval walls inside a meteorite crater

Climb the 90-metre tower of St. George's church in Nördlingen - the locals call it the Daniel - and a strange truth reveals itself: the gentle ring of low hills on the horizon is the rim of a crater. About fifteen million years ago a meteorite struck here, and the town was later built inside the bowl it left behind. The tower itself is made of suevite, the shocked rock formed in that impact and studded with countless microscopic diamonds. A Swabian town of around 20,000 people in Bavaria, Nördlingen lies on the Romantic Road roughly 90 kilometres south-west of Nuremberg and about 145 kilometres north-west of Munich.

Down in the streets, the wonder is the wall. Nördlingen is one of only a handful of German towns that still keeps a completely closed circuit of fortifications - about 2.7 kilometres of covered rampart with five gates and eleven towers that visitors can walk the whole way round.

From royal court to free imperial city

First recorded in 898 as a Carolingian royal court, Nördlingen was acquired by Emperor Frederick II in 1215 and rose to be a Free Imperial City. Its position where the trade roads from Frankfurt and Würzburg met those from Nuremberg and Augsburg turned its Whitsun fair, first mentioned in 1219, into one of the great markets of southern Germany. Two battles of the Thirty Years' War were fought outside its walls in the seventeenth century, after which the town slipped into a quiet that, as so often, preserved it.

Crater science and old streets

The Ries Crater Museum explains the impact and displays a piece of moon rock from Apollo 16; American astronauts once trained in the surrounding geology. Within the walls stand the thirteenth-century town hall, the old hospital and the late-Gothic church, and a tower keeper still calls out across the rooftops each evening. Less crowded than Rothenburg or Dinkelsbühl, Nördlingen rewards travellers who like their history with a little science.