This communist behemoth is the heaviest building in the world and a legacy of a brutal regime.

Sofia's legislative center is continuously reinventing itself.

A striking symbol of the Bulgarian capital.

Baroque celebration of the end of the Great Plague of Vienna.

Some believe that the artist behind this whimsical statue inserted his own likeness as a way to discreetly flip the bird.

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

This 2,000-year-old Doric bridge is still open to pedestrian traffic to this day.

A 1,000-year-old church holds the bones of the Christian martyrs who died hiding inside it.

A collection of grotesques lines the walls of this Italian villa.

Leveled by an earthquake, this Italian village is now preserved as a massive concrete art project.

This amazingly preserved Doric temple was abandoned before it was ever completed.

"Stairs of the Turks", a chalky white cliff eroded conveniently into stairs, allowing for easy pillaging.

142 ceramic steps become a mosaic once a year.

Italian cave with exceptional acoustics and an unsavory history.

Giant topiary dog once played a role in a terrorist bomb plot.

Climb inside an iron crystal magnified 165 billion times its normal size.

A marvel of Byzantine engineering under the streets of Istanbul.

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

Heralded as the world's first theater, these ruins are often overlooked as they reside in the shadows of the Acropolis.

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

A black cat protests the City Guild in Riga's Old Town.

Walk along the medieval fortifications that have been protecting Tallinn since the 14th century.

Water and windows define this defensive Italian well.

Hundreds of prehistoric stones, arranged in perfect lines in a French field.