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

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

This gallery commissioned by Cardinal Spada is known for its magnificent optical illusion.

This ancient trail climbs the mountain where a Latin League cult worshipped Jupiter, its main deity.

Ancient ruins hidden underneath a modern luxury hotel.

This ancient market is often referred to as the oldest shopping mall in the world.

A mysterious chasm in the heart of the ancient Roman Forum, the Lacus Curtius was once believed to be a gateway to hell.

In Rome’s Jewish ghetto, a 200-year-old bakery still makes the neighborhood’s historic sweets.

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

The final resting place of the poets Shelley and Keats.

At the crypt of St. Mary of Eulogies and the Dead you are left alone to ponder mortality among piles of skulls.

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."

Many famous English poets including Elizabeth Barrett Browning are laid to rest at this Swiss-owned cemetery in Florence.

Memorials at a Florence railway station remember the citizens who were deported from Italy and sent to extermination camps.

The graveyard is filled with beautiful funerary art and boasts breathtaking views of Florence.

Drink wine handed out through a window as part of an age-old tradition.

The largest and most famous wax anatomical collection anywhere in the world.

Venice's "Island of the Mad."

As can be expected from a centuries old church built in a canal city, the undercroft of this house of worship is beautifully flooded.

This Venice bookstore has resigned itself to constant flooding by keeping its books in bathtubs and boats.

This woodland area is a lasting tribute to the Queen Mother.

A replica memorializes the site where women were punished after the last witchcraft trial in Ireland.

An Irish cemetery filled with victims of political strife and violent conflict, including the grave of Bobby Sands.