Trompe-l'œil (French for "trick the eye" from tromper - to deceive and l'œil - the eye; pronounced as "trom ploy") is an art technique involving extremely realistic imagery in order to create the optical illusion that the depicted objects really exist.
Although the phrase has its origin in the Baroque period, use of trompe-l'œil dates back much further. It was (and is) often employed in murals, and instances from Greek and Roman times are known, for instance from Pompeii. A typical trompe-l'œil mural might depict a window, door or hallway to optically enlarge a room. Wikipedia