A mural is any piece of artwork painted or applied directly on a wall, a ceiling or other permanent surfaces. A distinguishing characteristic of mural painting is that the architectural elements of the given space are harmoniously incorporated into the picture. Some wall paintings are painted on large canvases, which are then attached to the wall (e.g., with marouflage), but the technique has been commonly used since the late 19th century. 
Some murals date back as far as to the Late Stone Age or Upper Paleolithic times. Think Cave Paintings, (like the Cave Chauvet in the Ardeche, France), Egyptian Tomb Paintings (as in check out the recreation of King Tut's tomb), Minoan palaces, murals in Pompeii, the Juxtlahuaca Cave and the Oxtotitlán Cave.