Back in the day, I often went on long bike rides in the country on clear summer nights when the moon was full. I could see well enough once my eyes had dark-adapted, it was cooler, and there were fewer motor vehicles. And it was so quiet that I could hear interstates several miles away. So basically, I was mapping quiet places. Now there's an app for that.

Edit: Now we can have crowd-sourced maps of quiet places.