

Massive tunnels hollowing the earth under NY - stinos
http://gizmodo.com/5985618/incredible-images-of-the-new-massive-tunnels-hollowing-new-york-city

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stuaxo
Silly question, what's holding the rooves up of those big spaces, is it thick
concrete - or is it just very thick rock under NY ?

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stinos
good question actually, isn't really clear to me either. I assume it's just
the rock though, for a couple of reasons: looks like it in most pictures, the
amount and strength of concrete needed to hold the weight of what's above is
beyond imagination, last but not least: from the rock's point of view this
tunnel isn't all that massive but rather a small hole through it's body that
doesn't weaken it at all.

