View Larger Map Cold War bunkers, abandoned Tube stations, buried rivers, deep level shelters...London's concealed features are among its most intriguing. So, in age-old Londonist tradition, we've created a map to try and show what a hollow city this is. And we need your help. We've plotted the more obvious features - the Fleet River, Zone 1 ghost stations, the Kingsway telephone exchange, etc. But we know there's a lot more down there. Please use......