Why Chinese City Walls Were Square and European Castles Were Round

In most people's imagination, city walls were built to keep enemies out. But in China, city walls served a very different purpose — keeping people in. The Tang Dynasty capital of Chang'an was an eighty-four square kilometer rectangle, divided into one hundred and eight walled blocks. Nearly one million people lived inside a management grid where every gate closed at night and every movement was regulated. At the same time in Europe, Charlemagne — the most powerful ruler on the continent — governed from a stone fortress housing a few hundred people. The peasants lived outside. One side built square walls to contain entire populations. The other side built round castles to protect a single man. This was not a difference in style. It was a difference in logic. This episode explores why Chinese city walls and European castles look so different — and what that difference reveals about two civilizations' fundamentally different answers to the same question: who deserves to be protected?