Seen from the air, Nördlingen looks almost too neat to be real. A ring of medieval walls wraps around a circle of red-tiled roofs, with a tall church tower in the middle. And the whole town sits inside a vast, round basin stretching far beyond the walls.
That basin is a crater, and it wasn't made by a volcano. About 15 million years ago, an asteroid more than half a mile wide slammed into what is now Bavaria, Germany. It left a crater about 16 miles across, now called the Nördlinger Ries, and the town of Nördlingen was later built right inside it.
A Town With Deep Roots
Nördlingen first shows up in records in the year 898. In 1215, it was granted city rights and became an imperial city of the Holy Roman Empire, and its first city wall went up that same year. Sitting at the crossroads of major trade routes, it grew into a busy market town for grain, livestock, textiles, furs, and metal goods.
Today it's one of only a handful of towns in Germany whose city walls are still completely intact. About 20,000 people live there, and its historic center looks much as it did centuries ago. Other landmarks include a town hall dating back to the 13th century and the Spital, a former medieval hospital.
Everyone Thought It Was a Volcano
For a long time, scientists assumed the Ries basin was the remains of a volcano, or perhaps shaped by glaciers or shifting ground. It certainly looked like it could be volcanic. Early researchers debated its origins for generations, and the true answer would surprise just about everyone.
The mystery was solved in 1960, when scientists Eugene Shoemaker and Edward C. T. Chao proved it was made by a meteorite impact. Their key clue was a mineral called coesite, which normally forms only under the enormous shock pressures of an impact. Shoemaker had been encouraged even before that by St. George's Church in town, which is built from a local rock created by the impact.
Buildings Sprinkled With Diamonds
Here's the most dazzling part. When the asteroid hit, it struck a deposit of graphite, the same material in pencil lead. The incredible heat and pressure turned some of it into diamonds, an estimated 72,000 tons of them.
Don't grab a chisel just yet. The diamonds are tiny, all less than 0.2 millimeters across, far too small to see or sell. But local stone was quarried to build the town, so Nördlingen's buildings contain millions of these microscopic gems. In a sense, the whole town is a little bit of buried treasure, hidden in plain sight.
The church's 300-foot steeple, nicknamed Daniel, is made of an impact rock called suevite, which contains quartz that was shocked by the collision.
Training Ground for Moonwalkers
Because it's such a large, easy-to-reach impact crater, the Ries became a practice field for the space program. In August 1970, Apollo 14 astronauts Alan Shepard and Edgar Mitchell trained there, learning to study impact craters and rocks before heading to the Moon. Apollo 17 astronauts trained there, too.
There's even a Ries crater museum in the town's old tanners' quarter. So if you ever visit Bavaria, consider a stop in Nördlingen. Where else can you stroll medieval streets, stand inside an ancient crater, and walk past walls quietly sparkling with diamonds you'll never see?
