Try not to get slimed in Tribeca.

This abandoned subway station beneath the Waldorf-Astoria hotel is allegedly used to secretly transport presidents.

A terrific purveyor of natural history objects and curios.

A beautiful and abandoned New York subway station from 1904, complete with chandelier.

This daunting 1st century fortress was purportedly the site of one of the most dramatic revolts of the Jewish-Roman wars.

A 2,000-year-old wine press hidden in an overlooked park in Tel Aviv.

The maze-like transportation hub contains abandoned areas, derelict stores, and a resident bat colony.

Biblical beasts and endangered animal preservation come together in this Israeli zoo.

Sitting right on the border between East and West Jerusalem this modern art museum is in itself a symbol of Israel's hoped-for unity.

This nightmarish children's plaything was left grotesque to help kids conquer their fear.

Italian poet Dante Alighieri is entombed in this small mausoleum in Ravenna, and his hometown of Florence has never been too happy about it.

The oldest of Venice's plague quarantine stations, designed to keep the medieval city safe from disease.

Venice's "Island of the Mad."

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

Erotic art covers the walls of the largest ancient pleasure palace.

A tree that defies gravity grows in an ancient ruin.

A submerged archeological park still holds the wonders of a Roman Sodom.

A sulfuric hellscape in southern Italy.

The once forbidden "secret cabinet" of erotic art from excavations of Pompeii and Herculaneum.

These "anatomical machines" are only one of the many strange items in this Italian crypt.

This controversial Irish show cave is home to a massive formation known as the Great Stalactite.

This singular Irish dolmen is more Frank Lloyd Wright than upright stonehenge.

Just another ancient, mysterious Irish stone circle.

A tiny microvalley etched into the side of Knocknarea Mountain hides another world.