This strange seaside tower got its name from a wealthy eccentric who would hide coins among its stones.

Wild lights and sound effects turn a walk through some caves into an eye-popping 1960s tourist attraction.

An acoustic anomaly with a mysterious cause.

The largest self-built castle in the U.S., six decades in the making.

At this Denver landmark, the meals are compulsory, the sopapillas are complimentary, and the insanity is everywhere.

A modernist landscape of water and sci-fi concrete.

Odd outsider art installations surround a Gold Rush-era ghost town.

Frank Lloyd Wright's most iconic home dangles over a Pennsylvania waterfall.

This knobby, drooping New Orleans oak is a favorite place both for climbing and for meeting giraffes.

Whisper secrets in a busy station only to be heard on the other side of this acoustic arch.

The world's longest known cave system.

Once a mortuary that held the remains of Buffalo Bill, this Denver hotspot is now a death-fixated restaurant.

Ride the subways of yesteryear.

A heavenly experience, right here on Terra Firma.

Towering basalt columns, a creation of fire and ice.

This frequently-photographed waterfall takes only a short hike to visit.

Take a drunken tour inside the world's largest known geode.

With over 100 jam-packed rooms to explore plus elaborate tea services and events, the Mansion on O Street is a hidden treasure.

A self-built castle made by a mysterious man.

The rocks in this arid basin leave trails of movement behind them.

Long-abandoned trolley tunnels just a mile away from the White House are turning into an art space.

This naturally-sourced hot spring is now home to a clothing-optional resort.

A breathtaking array of ancient Pueblo structures and artifacts counterintuitively preserved by neglect.

Under a glass sidewalk lie the remains of some of Manhattan's oldest buildings.