Under creative commons best practice, we have provided attributions for images used on the site.

Image is from Herry Lawford under cc by 2.0 / no edits

Image is from Masahiro Ihara under cc by 2.0 / no edits

Image is from Alpha du Centaure under cc by 2.0 / no edits

Image is from Natalie Maynor under cc by 2.0 / no edits

Image is from Natalie Maynor under cc by 2.0 / no edits

Image is from USACE Afghanistan Engineer District under cc by 2.0 / no edits

Image is from Dave Lundy under cc by 2.0 / no edits

Image is from Toru Watanabe under cc by 2.0 / no edits

Image is from Himy Syed under cc by 2.0 / no edits

Image is from Robert Taylor under cc by 2.0 / no edits

Image is from Neal Jennings under cc by 2.0 / no edits

Image is from Chung Ho Leung under cc by 2.0 / no edits

Image is from Wilson Hui under cc by 2.0 / no edits

Image is from Emilian Robert Vicol under cc by 2.0 / no edits

Image is from Ralf Peter Reimann under cc by 2.0 / no edits

Image is from Rene Schwietzke under cc by 2.0 / no edits

Image is from Gavin St. Ours under cc by 2.0 / no edits

Image is from Marissa Anderson under cc by 2.0 / no edits

Image is from Nat Welch under cc by 2.0 / no edits

Image is from Jason Howie under cc by 2.0 / no edits

Image is from Johan Larsson under cc by 2.0 / no edits

Image is from Kristina D.C. Hoeppner under cc by 2.0 / no edits

Image is from Dean Morley under cc by 2.0 / no edits

Image is from Darren Hillman under cc by 2.0 / no edits

Image is from Adnan Islam under cc by 2.0 / no edits

Image is from Darren Flinders under cc by 2.0 / no edits

Image is from Nayu Kim under cc by 2.0 / no edits

Image is from Atli Harðarson under cc by 2.0 / no edits

Image is from Martin Sutherland under cc by 2.0 / no edits

Image is from Ray_from_LA under cc by 2.0 / no edits

Image is from Chris Billman under cc by 2.0 / no edits

Image is from Sam / Olai Ose / Skaervoy under cc by 2.0 / no edits

Image is from Corey M. Grenier under cc by 2.0 / no edits

Image is from Patrick Pielarski under cc by 2.0 / no edits

Image is from Charles Chan under cc by 2.0 / no edits

Image is from Sabrina & Brad under cc by 2.0 / no edits

Image is from Ivan Walsh under cc by 2.0 / no edits

Image is from Matt Paish under cc by 2.0 / no edits