A 12mm focal length is currently the widest rectilinear wide angle lens available for a full frame camera, and the Sigma 12-24mm zoom is the only lens available other than a Voigtlander 12mm, which introduces many other complications in its own right. This is a really fine, reasonably priced lens. I plan to do a full hands-on blog review of it soon.
I have been photographing this scene in the morning when there is a bright light on the background scene and part of the memorial, but deep shadows in the foreground area. This is where the extensive dynamic range of good digital cameras comes into play, and one of the main reasons I always shoot in 16-bit RAW.
Below is a representation of this scene with no post processing done to it to demonstrate the highlight to shadow range the camera must capture. So long as there is detail in all the areas the scene can be massaged into an even-toned image by darkening the highlights and opening the shadows. In the days of shooting transparency film with a 1, or at most 2, stop dynamic range, a scene like this would have required something like a split ND filters and a dead-on exposure to even come close to pulling it off. Today, with dynamic ranges having a 14-stop latitude in a camera like the D600, accomplishing this is a snap during post processing.