The world's longest tunnel with an undersea section.

Come for the boats, stay to explore the intriguing assortment of art.

An ancient Incan convent on Lake Titicaca's Island of the Moon.

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

This floating garden in the sky is straight out of a fairy tale, but the real thing is nothing short of magical.

Sited in an Inner Mongolian desert are the remnants of an important trade stop along the Silk Road.

Climb to the top of its spiral spire for spectacular views of Copenhagen.

This obscure walkway links Edinburgh’s Old Town with one of the city's prime vantage points.

Enormous sandstone towers loom within a Czech forest.

A rare surviving Victorian greenhouse designed specifically to house giant water lilies.

This lake’s emerald green waters are a spectacular sight, but it’s not a great place for a swim.

This ancient sword lay in a waterlogged tomb for 2,500 years, but managed to remain relatively untarnished and impressively sharp.

These Egyptian statues have survived for 3,400 years and were an acoustic wonder of the ancient world.

The ornate structure is part of a building boasting more marble than the Vatican.

A breathtaking array of ancient Pueblo structures and artifacts counterintuitively preserved by neglect.

Wondrous sandstone hoodoos where Native Americans collected clay for pottery, 9,000 years ago.

A well-preserved Ancestral Puebloan ruin tucked beneath a desert cliff.

The most southern point you can drive to in the Western Hemisphere.

The largest and best-preserved Roman amphitheater in Africa was designed to seat 35,000 people.

The ruins of a pre-Columbian fortress city so secure it held off the Spanish conquistadors for over 20 years.

The cluster of igloo-like domes forms the remains of an ancient burial ground.

The remnants of an early automobile route across shifting sand dunes can still be found in the deserts of Southern California.

This spectacular track has run continuously since 1882.

This famed Silk Road oasis was one of the largest cities in the world before it was destroyed by a Mongol horde.