Interesting series of tunnels in Italy between Savona and Altare.
Tunnel spiral
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© Bing Maps
By Hinkkanen @ 2005-07-22 13:10:24
kjfitz
@ 2005-07-22 13:15:00
They do that to gain altitude over a short distance. There's a neat pair of tunnels near the Canadian Glacir National Park that does two separate 360 degree loops entirely within the mountains on either side of a steep valley.