The warmest cave in the Ozarks features two seemingly bottomless lakes.

Twenty-year effort to raise a castle using tools and techniques from the 13th century is now abandoned in the Arkansas woods.

From a canyon-like gorge, more than 20 million gallons of water emerge every day, while a smaller spring drips down, creating the illusion of an endless, gentle waterfall.

First crafted during the 19th century, the mill was fully restored in 1983.

If there's another drive-through golf-cart bar in a bat-filled cave on top of a mountain, we don't know about it.

Away from the crowds of fishing enthusiasts, take a hike deep into the woods and journey into an eerie darkness.

Where the author wrote her beloved "Little House" books.

The creator of the Kewpie doll's former home has been turned into a museum celebrating her life and work.

In Edwin Hubble's hometown, a scale model of the groundbreaking telescope that was named in his honor.

The show pony of cave systems, Fantastic Caverns manages to live up to its name.

A 35-foot-tall fork stuck in the ground outside an office building in Missouri.

This former office building has been transformed into an immersive music venue and art space.

The largest historic preservation organization in the United States.

This elaborate estate contains a stunning marble aviary, a sunken conservatory, and a magnificent music room with a two-story pipe organ.

This hidden stream beneath Indianapolis makes an appearance in the best-selling novel "Underground Airlines."

This stately clubhouse has showcased German-American culture for over a century.

A hidden network of subterranean passageways lies tangled beneath Indianapolis' bustling City Market.

A park where you can watch the highway zoom past.

This Indianapolis landmark offers a secret panoramic view of the city. 

A 30-year-old Sycamore tree grown from a seed taken to the moon and back.

A medical facility that has been kept frozen in time.

This mysterious hill seems to pull objects uphill.

This multisensory alley has the ability to remind bustling citygoers to stop and smell the roses.

This former zinc operation has a 90-year toxic history.