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Season 4, episode 11. This player now records resume state for the active profile so browse, account, and detail pages can bring you back here quickly.
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The Great Wall of China.
Winding 6,000 kilometers through undulating mountains, it is said to be visible with the naked eye from the moon. But who called for the Great Wall's construction and how was it accomplished? Historians, engineers, and scientists explore one of the wonders of the ancient world.
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Episode 10: Observatories: Stonehenge to Space Telescopes