Amid skyscrapers and traffic exists this unique aquatic ecosystem.

A three-story copper skybridge connects two Manhattan buildings with Art Deco luxury.

An echo chamber with a waterfall wrapped around its base at the Embassy of Canada in Washington, D.C.

This seemingly out-of-place gas station by the Watergate hotel was once described as the most expensive gas station in the world.

The word "Watergate" will forever be associated with the infamous scandal in 1972, but this fountain is famous in its own right.

The only tennis court that falls under the jurisdiction of the central bank.

One of the most influential presidents in U.S. history wanted only this plain, elegant monument as his lasting memorial.

Theme park featuring miniature replicas of European monuments.

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

A little sculpture with a large wardrobe.

Live a night as a Byzantine King, with a minibar and private jacuzzi.

While not Turkey's deepest underground city, this subterranean redoubt is the largest.

The deepest underground city in Turkey was designed to protect 20,000 people behind massive stone doors.

In this historic region, homes and churches are carved into ancient volcanic rock formations.

Roman ruins top white travertine terraces formed by ancient hot springs.

A charming beach town in Turkey captures all the colors of the rainbow.

The ancient latrines of the Greeks, in all their public glory.

This famous city eluded concrete detection until the early 2000's.

Climb a steep hill in 90 seconds on the second-oldest urban subway in the world.

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

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

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

A fountain standing as a testament to a doomed alliance.

No one is sure if the world's fourth-largest diamond had been found in a rubbish heap or was pawned by Napoleon's mom.