To stand in the shadow of the past is a feeling unlike any other. That's why each year millions travel thousands of miles to see the world's most historic sites.

A monument like the Kremlin--where Peter the Great stored weapons used to fight Napoleon and Ivan the Great built a cathedral to serve as the seat of the Russian Orthodox Church--is a prime example of how historic structures provide a unique glimpse into a culture's evolution.

Machu Picchu is another. A testament to a civilization's ingenuity, Machu Picchu is a relic of 15th-century urban development. The Incan mountain citadel is surrounded by a tropical forest and is memorable for its engineered roads, buildings and defense walls.

In Pictures: 10 Must-See History-Making Sights...