The world's longest known cave system.

See the sky in a new way through this art installation.

A curious fountain that has no water and includes Satan, a crab, and 9 giraffes.

Mysterious 500-year-old tapestries depict a unicorn hunt.

World War II bunker still standing on the New Jersey beach.

A giant Troll lurks under one of Seattle's oldest bridges.

Statue of Lenin, from Cold War era Czechoslovakia, now in a neighborhood of Seattle.

A museum dedicated to the history and exploration of both popular music and science fiction.

Venice's island of the dead.

Go inside to really appreciate this 500-year-old technological masterpiece.

Breathtaking and huge 430 year old maps of Italy.

A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.

Hundreds of lucky felines haunt the ruins where Caesar was murdered.

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

2300-year-old Roman road connecting the empire.

Hear the quietest sound from across the dome.

Famously misunderstood wonder of the ancient world

England's oldest surviving hedge maze has been confusing visitors for over 300 years.

Ancient Egyptian wigs, South American feather headdresses, a bounty of anthropological artifacts in Oxford.

A theatre built to house the rowdy Oxford graduation ceremonies became the stage for a debate about God's existence.

A modern zoetrope on the New York City subway.

An artist's cute bronze subway sculptures belie his violent artistic past.

The most confusing clock in New York.

Elevated freight railway turned wildly successful urban park.