A parody site created back in the 1990s claims there's a giant underwater city within "the crystal clear waters of the Minnesota River." And people have been visiting from as far away as Texas to discover the Atlantis of Minnesota.
I love the "official Mankato, MN web page", which was created in 1996 by Don Descy, an educational studies professor at Minnesota State University — to teach his students not to believe everything they read on the Internet. The site includes lush descriptions and blurry pictures, in that telltale mid-1990s "free website" style, of the Mankato underwater city:
"Recent discoveries have pointed to the building of this city about 4000 B.C.," says Dr. Seymour Bottoms, world famous astrogeologist at Mankato State University. "At this time early Indians settled in the Emerald Green Valley and built the city next to the Minnesota River. The city was covered with water in about 1256 B.C. when the first of a series of major earth tremors shook the region."
And yes, the professor happens to be named Seymour Bottoms. Why do you ask? People in academia don't discriminate in hiring or tenure decisions purely based on their colleagues' porno joke names. The site also mentions a mysterious pyramid in Mankato and hints that aliens have visited the town.
The site claims to have had nearly 1.8 million visitors, which is plausible since it was a Yahoo Pick Of The Week in 1996 and has been featured in the local media constantly. We only discovered it for the first time last week, while working on the piece about weird urban ecosystems. We quickly sussed out that it was a joke site, but apparently others haven't been so discerning.