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

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.

Legacy of the earthquake that nearly wiped Lisbon off the face of the Earth.

A unique seaside cave where Aleister Crowley faked his own death.

This small chapel is built of human bones and decorated with a golden skeleton.

Italian cave with exceptional acoustics and an unsavory history.

A mysterious ancient elephant said to possess magic powers is now the symbol of a Sicilian city.

The world's most active stratovolcano is almost always erupting.

Two very green residential towers cleaning the air in one of Europe's most polluted cities.

A random tree outside a Budapest hotel has become a DIY shrine to the late singer.

The Cycladic architecture makes this Athens neighborhood feel like an island paradise hidden in the shadow of the Acropolis.

This gem is often wrongly overshadowed by the larger, newer Metropolis church in Athens.

This building displays the scars of the “Dekemvriana,” a dark time in modern Greek history.

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

A Byzantine-era church hidden in a wooded area below the Acropolis.

Once the home of a hermetic monk, this cave now houses a small church.

An Orthodox church built by the Royal Family for the Russian community exiled to the French Riviera.

A small island less than half a mile from Venice is a forbidden island with a dark and twisted past.

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

Thanks to its heroic service during WWII this Soviet castle has been turned into a monument towered over by a brutalist titan.

A striking Soviet memorial commemorates the liberation of Belarus from the Nazis.

A sculpture of graceful storks sits atop this fountain in Independence Square.

Remnants of the city's Soviet history hover over this modern fast-food outlet.