These haunting ruins of a 700-year-old Prehispanic city have witnessed centuries of wars and massacres.

A disquieting Aztec sculpture displays hundreds of stone skulls representing the victims of human sacrifice.

This colossal ancient jaguar sculpture was used as a vessel for the hearts torn from sacrificial victims.

The singular ruins of a mysterious lost city.

Ancient barriers wrap around what was once an important stop along the Silk Road.

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

The elliptical citadel resisted the advance of the mighty Ottomans several times, thanks to the military prowess of the "Dragon of Albania."

This ominous Albanian fortress houses tanks and downed planes as a reminder of their victories over Western imperialism.

A naturally beautiful, seemingly bottomless deep blue spring.

Color-coded signs direct drivers on a network of routes designed to avoid Pittsburgh traffic.

Bolivia's needle-like rock formations.

Sections of the iconic limestone columns have been left uncleaned as a reminder of the city's polluted past.

A curious fountain that has no water and includes Satan, a crab, and 9 giraffes.

The "Seinfeld" diner.

Every equinox this Maya pyramid puts on a spooky ancient light show.

No telescopes, no power, no gift shop: The Observatory of Chichen Itza, one of the world's oldest observatories, takes astronomy back to basics.

Frank Lloyd Wright’s most iconic home dangles over a Pennsylvania waterfall.

A former major munitions plant that has been converted into a sprawling art space.

At 207 feet, one of the world's longest continuous escalators.

The beloved statue at the National Academy of Sciences is oh so inviting to sit on.

A tiny piece of the Moon is embedded in this stained glass masterpiece.

The sci-fi villain is a little-known inhabitant of the U.S. capital's largest cathedral.

The only way to see Pittsburgh is from the top of this lookout point, just like the ancient members of the native peoples did.

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