These spectacular, symbolic serpents lie within the shadow of the Great Temple.

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

The unique waterfall in Iceland's south features a backdrop of geometric black lava columns.

Medicinal spa created from the mineral-rich runoff of a geothermal power plant

A chain of 16 wondrous lakes formed as a result of the gradual dissolution of soluble layers of bedrock.

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

An unfinished tomb carved into a giant boulder in the Arabian Desert.

The second largest monolith in the world was once betrayed by its lover, Ben Aicha.

Every winter, this former planetarium is transformed into a massive, brightly-lit Christmas ornament.

Visit the site of a subway powered by nothing more than air--and lots of it.

Thousands of colorful pirogues showcase ingenious craftsmanship at the largest fishermen port in Nouakchott.

The largest camel market in West Africa

A geological bull's-eye visible from outer space.

This remarkably well-preserved mosque stands amid an 11th-century caravansary.

An architectural relic that survived the hands of time.

Five ancient libraries, little changed for centuries, preserve a medieval archive of Quranic lore and civic documents

Climb atop one of the world's longest and heaviest trains for an unbelievable journey across the Sahara Desert.

An 18th century wonder of the world, lost in WWII, re-created at the Catherine Palace.

The oldest museum in Russia is home to a fascinating collection of nearly two million anthropological artifacts and anatomical curiosities.

Palace where the nearly un-killable Rasputin was murdered.

A 250-year-old timepiece-automaton adorned with golden mechanical birds, which still sing to this day.

Moscow's other, lesser known kremlin is a fairytale-like cultural complex modeled after Old Russia.

An iconic Soviet statue of working-class people.

Moscow's imposing monument to the Space Age.