Nördlinger Ries

Location: Western Bavaria, Germany

Diameter: 24 kilometres (15 miles) Depth: 100 metres (330 feet) Age: 15 million years

Remarkably, the Ries crater contains a city – Nördlingen – within the structure’s inner ring, and the full impact of the crater can only be seen when viewed from the air. While the inner ring is highlighted by the town walls, the rest of the crater has been eroded away and isn’t immediately visible. The crater’s existence probably eluded the medieval Europeans, who unknowingly matched their town walls to the inner crater ring

approximately one kilometre (0.6 miles) in diameter – likely the same dimensions as the crater-forming meteorite.

The true origins of the crater also eluded residents of Nördlingen for over 100 years. It was long believed the Ries structure was an extinct volcanic crater, but when geologists Eugene Shoemaker and Edward Chao visited the town in the 1960s, they found overwhelming evidence that Ries was an impact crater.