The excavation will descend over 50 feet below the surface say reports, deeper than the height of nearby houses, and will feature a 45-foot swimming pool, hot tub, sauna, massage room, ballroom, covered courtyards, staff accommodation, parking, a turning circle and car lift.
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Tubes, trains, trams, buses, cable cars, river buses, taxis and going by foot - your guide to getting around during the strike.
Union officials rejected a revised offer from Underground managers during a meeting at the conciliation service ACAS this afternoon.
Train drivers were offered £200 a shift to work on the new 'Night Tube' in a bid to halt the threatened walkout.