Niagara Cave

On Minnesota’s southern border (hundreds of miles west of the far more famous “Niagara”) is a geological spectacle known as Niagara Cave. The grotto is among the largest in the Midwest, and is home to a 60-foot subterranean waterfall, 100-foot-high ceilings, ancient fossils, unusual limestone rock formations, calcite flowstone, an echo chamber, and even a wedding chapel for the adventurous affianced.

The cave was discovered in 1924, when legend has it that three pigs disappeared from a nearby farm and ended up in a sinkhole. When their owner went looking for the wayward swine, he not only found his livestock—alive and well, 75 feet underground—he also discovered the underground chamber and its many wonders. Public tours started about 10 years later.

While the cavern itself is likely millions of years old, Niagara Cave has a 21st-century claim to fame. In 2015 it became the first commercial cave in the world whose energy use is 100 percent offset by solar energy—its large photovoltaic solar panel array produces around 45,000 kilowatts of energy per year.

Visitors to the cave can embark on hour-long guided tours, consisting of a mile-long hike through the underground marvel. Outside the cave, visitors can also pan for gemstones in a manmade trough, play mini golf, picnic, and of course, shop.