In western Washington state, the prairie looks like bubble-wrap, dotted with millions of 8 foot-high mounds some 30' in diameter. The so-called Mima Mounds have been a source of mystery for over a century and a half. Who could have built them? And why?
They were thought to be Indian burial mounds, but no relics could be found. Lots of other explanations were considered and discarded, but it appears that the builders have been revealed - and it's gophers.