One of the tallest buildings in Iceland, and perhaps, the most visually impressive.

Ruined 11th century abbey built by King David I in Edinburgh, Scotland.

A verdant 17th-century-style garden hidden along Edinburgh’s Royal Mile.

This 17th-century street hidden beneath Edinburgh was once a breeding ground for the black death.

1513 Turkish world map, full of European state secrets and snarky commentary.

A marvel of Byzantine engineering under the streets of Istanbul.

Long hidden under grime, the politically radical murals of a little known Yugoslavian master are finally getting their due.

Found art has transformed this Pittsburgh neighborhood into a psychedelic dream.

Pittsburgh’s largest and most detailed model train display began as one WWI veteran’s hobby.

There aren't too many operational funiculars around, but Pittsburgh has two!

A model of a dinosaur that was named for Andrew Carnegie stands outside the museum that also bears his name.

A quiet, gothic haven nestled between Pittsburgh's Squirrel Hill and Point Breeze neighborhoods.

This historic Pittsburgh tennis complex is a rare example of natural red clay courts.

These disused steel furnaces are now haunting ruins that may one day be a national park.

A stone arch leads to a cavernous 1930s spring house tucked away in the Pennsylvania woods.

Where hikers on the Tecumseh Trail can exchange a dirty sock for a free geode.

The "Prussian Versailles" that is as glorious today as when it was built.

An imperial church bombed to ruins during WWII now stands as a jagged memorial.

An astonishingly accurate water clock that doubles as an hourly spectacle in this Berlin shopping area.

The world's first clock to use set theory as a measure of time required the invention of a new light bulb just to maintain its obtuse measurements.

A monument to the three wars that led to German unification towers within a Berlin traffic circle.