That's the Ries Crater. It went undetected until David Shoemaker noticed the stones used to build the cathedral, and realized they included shocked quartz, which would only be present in rock as a result of a nuclear explosion (he found the stuff in the sand, after the test at Trinity) or from an asteroid impact. He and his colleague then realized that the entire valley in which this town and cathedral were located WAS the impact crater!
Have the scientist found shocked quartz at this impact site?