Tunnels, treehouses and tensegrity towers: landmarks in protest architecture, from UCLA to Hong Kong

In his 1868 street-fighting manual, Instructions for an Armed Uprising, the French revolutionary Auguste Blanqui sets out meticulous instructions for how to build a good barricade. Such defences, he wrote, must no longer be thrown together in "a confused and disorderly fashion", but should be robustly composed of two sturdy rampart walls made of paving stones and plaster. All the aspiring revolutionary needed was a good supply of cobblestones and "a cart filled with sacks of plaster, plus wheelbarrows, handcarts, levers, picks, shovels, mattocks, hammers, cold chisels, trowels, buckets and troughs". Blanqui advised that all of these things could be…