My son (12) sending some WW2 explosion craters

Where we live there are loads of WW2 explosion craters throughout the forest. Legend has it an allied squadron had orders to bomb the city (Vienna), but the war was kind of over so they decided not to destroy the pretty city so they dropped the load in the hills nearby. I don't know if it's true or there's a different story to it but we sure have fun shredding all the craters all these years later!