Actually this isn't really a FAQ... just the answers to unwritten and un-asked questions.
This is a series of photographs of artworks from tunnels.
Each piece of art was found on the interior wall (and/or floor or ceiling) of a tunnel or bridge; each was beneath a roof. All of the tunnels can be passed through on foot, though many may also be accessed by bicycle, horse, car or boat.
I make no distinction between graffiti and permitted artworks.
In fact I think the boundaries between commissioned murals and graffiti are quite unclear, and frequently the status of a certain image is not obvious.
By the nature and position of these works, they must express their intent without any explanation. Therefore I provide no description or commentary of them other than stating their general location.
The copyright status of most of these works is unclear. As my photographs typically show more than simply a reproduction of the image, I assert copyright over these. Should I find out the original artist of an image, I will additionally indicate this.