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

The ancient dwellings of the Puebloans, located in the cliffs of majestic mesas.

The clock that sets them all.

Ruined pieces of stone and a swimming pool are all that remain of an amusement park swept away by a flood.

The remains of a chapel created for convenience.

One of Savannah's oldest and most haunted cemeteries, featuring graves desecrated by Sherman's Union Army.

This set of rickety spaceships are prepared to give alien travelers a place to relax and go to the bathroom.

The world's largest fire hydrant is supposedly tornado-proof.

This psychedelic tromp l'oeil seems to be beckoning drivers to crash into a wall.

This titanic steel chain linking two buildings was installed without permission but instantly beloved.

This natural spring not only claims to heal the wounded but it has also been willed to God.

The language and heritage of a nearly forgotten culture can still be explored in this Southern enclave.

Settled in 1696, abandoned after the Revolutionary War.

This bare tree might not have leaves but it is constantly clothed in festive decorations left by mysterious local benefactors.

"X" marks the spot of an echo chamber in the middle of a plaza.

This haunting tombstone comes complete with a heartbreaking story of love and loss.

"Not too many people can say they've had a nuclear bomb dropped on them, not too many would want to." — Walter Gregg.

A life-sized memorial to Harry L. Collins, the official corporate magician of Frito-Lay.

One of the first historical sites of an alternative universe was installed in the town of Paris, Illinois—which is now home to an annual spelling bee of Kcymaerxthaereal words.

The only remnant of a small mining town is an abandoned railroad tunnel that is steeped in ghostly lore.

The largest earthwork effigy in the world.

A real flying saucer, contracted by the U.S. Air Force.

This stuffed pigeon of war had the very serious name "John Silver" until he lost a leg in battle.

A miniature world of concrete and stone in Springfield, Ohio.