Tunnels Everywhere
An unusual document of unexpected interest to urban explorers was recently released by the CIA. The Clandestine Services History - Berlin Tunnel Operation, 1952-1956 (large PDF) details, among other things, the methods used to construct a covert tunnel into East Berlin to “tap” East German and Soviet communication lines. Inspirational reading, perhaps, for the Twin Cities explorers digging their own tunnels beneath Minneapolis, and entertaining reading for everyone else.
