A mural is painted directly onto a surface such as a wall, ceiling, or sometimes a floor, or on a prepared panel or canvas that is later affixed to a wall. The most common surfaces are interior and exterior walls made of plaster, brick, concrete, or wood, but murals can also be applied to other sturdy substrates or prepared panels. What the user asked: “surface on which a mural is painted.” Direct answer:

• Primary surfaces: walls (plaster, brick, concrete), ceilings, and sometimes floors or prepared panels attached to walls.
• Common preparation: ensure the surface is structurally sound, clean, and suitably primed for the chosen paint or medium; exterior walls may require sealants and weatherproofing.

If you want, I can tailor this to a specific mural project (indoor vs outdoor, wall material, or the painting medium) or provide guidance on surface preparation steps for a brick wall, concrete, or drywall.