Summary
Syrians wage 'war of tunnels' for Damascus
Guided more by what they can hear than see, Syrian troops and rebels are battling in the bowels of Damascus, digging tunnels in a campaign to control the eastern entrance to the capital.
Inside an empty building, a hole in the floor leads to an observation room 7 meters down, where army computers are linked to cameras rigged up inside a network of army tunnels.
For the army there are two red lines -- Abbasid Square and Jobar's March 8 Tower, which would allow rebel snipers to target much of eastern Damascus if captured.
Several months ago the army discovered a rebel tunnel that ran behind their lines, and managed to thwart "a massive attack on Damascus" at the last minute, the colonel says.
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