A peace symbol in Northern Ireland is among the world's largest hedge mazes.

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

The longest hedge maze in the world.

A complex, nine-layer maze on the grounds of a Venetian doge's playground.

Venice's "Island of the Mad."

Venice's island of the dead.

Traditional 11th-century outdoor tannery.

The university library shaped like a giant piece of Swiss cheese.

These gutted monastery ruins still stand proudly in the middle of the Italian countryside.

A Prada store in the West Texas desert that is never open for business.

The largest drain hole in the world.

360° views of the city plus five floors of optical illusions and hands-on science.

This 16th-century monastery has been turned into a surrealist architecture compound.

Water and windows define this defensive Italian well.

A 16th-century horror show built in a lovely Italian garden.

The Pope’s secret escape route.

The final resting place of the poets Shelley and Keats.

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

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

Installed in an act of one-upsmanship, the annual sundial in this church is also a symbolic victory for the Gregorian calendar.

Rome's semi-secret peephole vista is also a former Crusader stronghold.

An alchemist's "magic door" stands in the middle of a Roman park.

This hill made entirely of ancient Roman jars was simply a garbage dump to the people of the time.

An Italian crevasse filled with abandoned buildings gives visitors a look at the world without humans.