Discover the Great Wall of China

Construction technique changed dramatically over the wall's history. The earliest sections were built from rammed earth -- soil compacted in layers between wooden forms -- a fast, cheap method suited to the wall's original scale. The Ming dynasty's rebuilding introduced brick and dressed stone facing over compacted earth or rubble cores, a far more durable technique that's why most of the wall still standing today dates from that period rather than earlier ones.

Ming-era construction added regularly spaced watchtowers, used for signaling (smoke by day, fire by night) between garrisons over long distances, along with fortified passes at strategic points where the wall crossed mountain gaps or major routes -- Juyongguan and Jiayuguan among the best known.

The wall's route itself was a deliberate engineering choice as much as a defensive one -- built along mountain ridgelines wherever possible, using the terrain's own steepness as a force multiplier rather than relying on height and thickness alone.