Toward the end of World War II, Allied planes dropped tens of thousands of bombs on a region of Germany that’s now part of Poland, and the devastation is recorded in thousands of craters that remain to this day. 

Researchers recently mapped and analyzed the deeply scarred landscape for the first time, counting around 6,000 bomb craters ranging from 16 to 49 feet (5 to 15 meters) in diameter. Some areas held as many as 30 craters in a single hectare (10,000 square meters).