From thorn hedges and rammed earth to concrete barricades and digital firewalls, humanity has always loved a good line in the sand. We build walls to feel safe, to mark belonging, to keep danger, difference, or desire on the other side. And sooner or later, every one of them cracks.

In Humpty Dumpty, this sharp-eyed and curious tour of human history traces thirty walls that once promised permanence. Some stretched for thousands of kilometers, others barely ringed a city. All were built with confidence. None were forever. From imperial megastructures and forgotten frontier lines to border fences, city walls, and psychological barricades, this book explores what walls reveal about fear, power, ambition, and imagination.

These are not just stories of stone and soil, but of the people who raised them, guarded them, tunneled under them, climbed over them, and finally abandoned them. Along the way, legendary walls and half-built defenses haunt the margins, reminding us that even the idea of a wall can shape history.

Part global history, part cultural archaeology, Humpty Dumpty asks a simple question with unsettling consequences: if walls always fall, why do we keep building them?