We visited the village of Cu Chi (loosely pronounced as "Gucci") where there is an elaborate tunnel network used by the Vietcong during the War of Liberation from the American forces. No one actually knows how such a network originated. The schematic shows a cross-section of one of the tunnels. There could be many layers like 4 shown here. If a bomb were to destroy the first layer, the soldiers could evacuate to another lower down. There is an escape route out to the Saigon River (extreme right). The kitchen has compartments in which smoke is relayed until it eventually comes out around 100 m away and merges with the mist or fog. Even if a grenade were to be lobbed in thru that exit, no harm would come to the kitchen and its occupants. Interesting to note that there is a bottleneck which prevents American soldiers to crawl thru for their sheer size. Many lessons to be learnt from the "Vietcong University" indeed!