The wonderful Canon TS-E 24mm f/3.5 L it's the mos famous architecture lens by Canon.
It is a tilt-shift, wide-angle prime lens that provides the equivalent of the corresponding view camera front movements on Canon EOS camera bodies.
Shifting allows adjusting the position of the subject in the image area without changing the camera angle; it is often used to avoid convergence of parallel lines, such as when photographing a tall building. Tilting the lens relies on the Scheimpflug principle to rotate the plane of focus away from parallel to the image plane; this can be used either to have all parts of an inclined subject sharply rendered, or to restrict sharpness to a small part of a scene. Tilting the lens results in a wedge-shaped depth of field that may be a better fit to some scenes than the depth of field between two parallel planes that results without tilt.
Unlike most view cameras, the shift mechanism allows shifts along only one axis, and the tilt mechanism allows tilts about only one axis; however, the rotation of the mechanisms allows the orientations of the axes to be changed, providing, in effect, combined tilt and swing, and combined rise/fall and lateral shift.