Ancient serpentine sacrifice holder that has stood the test of time.

A fountain standing as a testament to a doomed alliance.

The most metal church of all time was built in record time because of an international, pious pissing contest.

A marvel of Byzantine engineering under the streets of Istanbul.

A sixth-century Byzantine cistern hidden below a modern carpet store.

This crucial gathering spot along the "hippie trail" still displays old notes between traveling beatniks and backpackers.

Taking the subway here means doing so over a bridge located in the middle of an estuary.

Five sultans and their families rest in eternal splendor, teeming with overlooked beauty and drama.

A small etching on the white marble parapet was written in runic script by a Viking mercenary.

This remarkably well-preserved Egyptian plinth is pretty well traveled for a giant piece of stone.

Over the centuries, this island paradise has done it all, from providing monks with ecclesiastical respite to sheltering an exiled Leon Trotsky.

One of the largest wooden constructions in Europe was meant to be a casino, but soon became an orphanage.

A NATO bombing took the lives of 16 civilians in 1999—the ruins remain in the center of Belgrade.

This abandoned but well-preserved Prussian fortress sits abandoned in a Polish forest near the German border.

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

The medieval ferry service has been going strong since the 14th century.

A purr-fectly spirited bronze celebration of local street felines through history.

A black sand beach where glacial fragments wash ashore and look like sparkling diamonds.

The tradition of open-air secondhand and antiquarian bookselling in Paris dates back to the Renaissance.

A helicopter memorial commemorating what was once the only way to access this West Berlin exclave.

Tacoma's historic Beaux-Arts train station is now a federal courthouse featuring large-scale glass sculptures by artist Dale Chihuly.

Poland's oldest surviving university building holds a wealth of historic science instruments including some used by Copernicus.

In 1958, an MIT fraternity pledge laid down on this bridge and instituted a new, unique unit of measurement.

This bridge was the birthplace of a unit of measurement based on a fraternity joke.