This invisible city follows different laws of planning to its surface counterpart. Its tunnelled streets often kink and wriggle, or run to dead ends. Some of them curl back on themselves like whips. At junctions, three or four tunnel-streets might spray out. There are slender highways running almost the length of the tiled map, from southwest to northeast. There are inexplicably broken grids of streets, or hubs where the spokes of different tunnels meet. Coming off some of the tunnels are chambers, irregular in their outlines and with dozens of small connecting rooms. – The New Yorker