Tunneled...

"A friend and I were on our last day of a 7 day bike tour across Wisconsin and back, and I snapped this photo at the end of a series of three tunnels on the Elroy-Sparta State Trail in Southwest Wisconsin. This tunnel in particular was the longest of the three, spanning almost a mile and emitting cool, humid air 24 hours a day". Taken by Daniel Murphy

Western Wall Tunnels

"This is part of an underground tunnel exposing the Western Wall in its full length. The carved stones in the bottom are original from the Temple... I walked there with a large tripod, it was awkward and uncomfortable but paid off! I wanted to capture the atmosphere of that special and interesting place with no additional artificial light". Taken by Flavio

...when darkness meets the light gods

Taken by Man Underground

Atomium

Atomium, Brussels, Belgium. Taken by Peter Gutierrez