December 1914. After 5 months of war, both the Germans and the Allies have dug themselves in behind impenetrable lines. Faced with this siege, the soldiers will bring back into use an old weapon that they will modernize: mines, blowing up enemy fortifications from beneath... In February 1915, it’s at the foot of a small Flamish hill (Hill 60) that this mine warfare will really start, at the initiative of the British Forces and units specially trained for this type of operation, the tunnelling companies. During the summer of 1916, whilst the New Zealand tunnellers were digging out mine tunnels under the Arras suburbs, they discovered immense quarries. These soon served to shelter 24 000 British soldiers as they prepared their attack on German positions. This subterranean war will come to a climax during the Battle of Messines, where 470 tonnes of explosives shared out between 19 mines were used to cause the greatest explosion ever created by man at that time. Thanks to explanations from world-class experts, computer generated images, re-enactments, and historical archives, you can now discover the incredible underground megastructures of the First World War.