A tiny Greek Orthodox church from the Ottoman era hides on a busy city street.

These caves secretly held national treasures during World War II.

Where commuters walk through remnants of an ancient Greek necropolis.

The ruined doorway is a portal to the building's turbulent and torturous past.

Legend says this sacred tree was a gift from goddess Athena.

An ancient octagonal weather station named for the eight Greek gods of wind.

Nelson Mandela lived here with his family from 1946 until his arrest in 1962.

Two giant painted cooling towers make for one of the world’s most epic bungee jumps.

Raging waters have created a strange geological site that looks like something off of a progressive rock album cover.

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

This Roman amphitheatre was also the location of the first gladiator school.

Southern Italy's spinning top village.

Unscathed for almost 2,000 years, the best preserved Roman triumphal arch is in a small southern Italian city.

Skulls and skeletons are omnipresent in this church dedicated to souls trapped in purgatory.

People have been living in the cave houses on this Italian hillside since the Neolithic era.

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

A forgotten "city of water" underneath the famous Trevi district.

Wedding chapel's mysterious spiral staircase said to be miraculously constructed.

An immersive environment that is part haunted house, part choose-your-own-adventure, and part jungle gym.

Once a lonely sentinel on the edge of the Great Plains, this rebuilt trading fort offers a glimpse of life on the Santa Fe Trail.

A king's pet, a pope's gift, an artist's inspiration, and a tragic shipwreck.

Elaborately carved to showcase the glorious wealth that the age of exploration brought to the Portuguese empire.

The world's oldest bookshop still in operation.

A 16th century chapel decorated with bones, skulls, and entire bodies hanging from the wall.