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

A Trabant car, a kangaroo statue, and a plethora of plants take over this abandoned-factory-turned-bar.

A series of playful yellow penguins share a serious message about the environment.

A turn of the century building boasting some of the most beautiful art nouveau architecture in Prague.

A trail of iron footwear stands as a monument to the thousands executed along this riverbank during WWII.

Built in 1870 at the bridge that connected Buda and Pest, this spectacular incline railway was almost lost forever during World War II.

Macabre astrological automaton clock dating to the late 1400s.

Despite attempts by local police to discourage it, Beatles-inspired graffiti has been a means for artists to air grievances for decades.

Two stunning 17th-century libraries and a cabinet of curiosities.

This staircase in a lush tropical grotto was built by enslaved laborers and renamed to honor Queen Victoria's role in ending slavery in the British Empire.

The last of Philadelphia's wood-paved streets is now a landmark of terrible engineering.

This elaborate towering structure was once famed for its revolutionary height.

This charming colonial alleyway is one of the oldest continuously used residential streets in the U.S.

The oldest surviving botanic garden in the United States.

Yo, Adrian!

Dr Barnes' $25 billion private collection of art and arboretum.

Several times a year, during low tide, two pairs of historic train tracks are revealed on this New Jersey beach.

These unassuming lighthouses have seen the first reading of the Pledge of Allegiance, the first wireless transmission, and more than one mystery.

The only museum with its curator—and her pets—buried inside.

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

This historic "City of the Dead" lies prominently in the center of New Orleans' famous Garden District.

The second oldest continuously operating bar in Louisiana.

Eccentric concrete mansion and museum designed and built by hand from the inside out.

The last moments of the ill-fated Pompeiians, frozen forever in plaster.