This Industrial Age architectural and engineering gem helps visitors and residents alike traverse Lisbon, “The City of Seven Hills.”

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

This palatial spiral staircase was so unusual the name "snail" was given to the noble family who built it.

A new sculpture calls attention to climate change in the centuries-old city it threatens.

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

Thousand-year-old Viking runes adorn an ancient Greek lion at the entrance to the Venetian Arsenal.

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 Roman statue is missing a limb from when the Venetians stole it from Constantinople during the Crusades.

One of the tallest lighthouses in the world also serves as a monument to the fallen of World War I.

This historic floating crane became an unlikely symbol of the port of Trieste.

A cone-shaped top and cylindrical body set this 900-year-old structure apart from other Italian bell towers.

Meet the oldest inhabitants of this Italian hamlet, a series of oddly preserved mummies.

Two bronze wolves atop this large rock honor the "Wolves of Tuscany" brigade of World War I.

Numerous stone coffins from different centuries, lined up in a sixth century basilica.

The tomb of the mythological founder of Padua is not hidden in some obscure crypt, but stands right in the middle of the city square.

A miniature train-ride through Slovenia's largest cave system.

This massive subterranean fissure is known as the "underground Grand Canyon."

A sinister pyramid in the Frari contains the heart of the famous neoclassical sculptor.

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

During World War II, this rice mill became a Nazi concentration camp.

The Adriatic's most famous wind can be reliably experienced in the city's Marina.

This overgrown mountain village has been abandoned for nearly a century.

When a massive landslide hit one of the world's tallest dams it created a tragic environmental disaster.

In the world's oldest university is a stunning 17th century anatomical theater carved from spruce.