Recognized the world over as the home of the McCallisters in the 1990 movie "Home Alone."

This old ruin once served as a post office, a train station, a restaurant, and a bridge to the Atomic Age.

Like a kitschy mirage in the Mojave, this eatery serves up classic 50s-style diner meals and a dinosaur sculpture garden.

The "world's biggest dinosaur" once housed a creationist museum in its abdomen.

With 3,000 bikes on display, the world's largest bicycle museum includes some famous rarities.

The perfectly preserved underground rooms where Churchill plotted the war against Germany.

This underground holding cell was forgotten for over a century and rediscovered in the 1960s.

Artifacts from a battleship sunk at Pearl Harbor displayed in the Capitol building of its namesake.

Hidden in the hills of Western Pennsylvania lies one of the best-kept ghost towns in America that you can legally visit.

The last moments of the ill-fated Pompeiians, frozen forever in plaster.

This private skyway is filled with art and was expanded explicitly so that Hitler could appreciate a river.

Ever hear of the Milazzo Cage?

A colossal aqueduct from the second century B.C., deeply hidden in a gorge on the outskirts of Rome.

Hidden within this iconic mountain are a set of World War II bunkers once used by German forces.

This park on the outskirts of Rome boasts two ancient Roman aqueducts and a medieval tower.

The ruins of the largest gladiatorial school in Rome are largely hidden under modern streets.

In the early Roman Empire, people deemed traitors and criminals were tossed to their deaths from this rock.

This is the oldest Roman-made bridge in the city still existing in its original state.

This curious, round temple is the oldest still-standing marble building in Rome.

Ancient ruins hidden underneath a modern luxury hotel.

Rome's ancient Etruscan rival, now a park full of ruins.

Brass cobblestones mark the places where individual Holocaust victims were taken from their homes.

The spot where the fascist dictator made some of his most famous speeches including declaring war on Britain and France.

This large, circular tomb is the final resting place of the first emperor of Rome.