The abandoned sections of the Turnpike might be a bit too well-known, actually. There are hundreds, probably thousands of abandoned rail tunnels in the United States, especially after the big consolidations of the rail industry.
http://www.waymarking.com/cat/detail...d-79e4f400ec31
https://www.google.com/#q=abandoned+rail+tunnels
http://www.abandonedrails.com/Donner_Pass
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Michael B.