Marcel Duchamp, 1917. A urinal signed 'R. Mutt' — not a painting per se but the most influential 20th-century artwork by every poll. Tate / Pompidou replicas.
From Wikipedia
A fountain, from the Latin "fons", meaning source or spring, is a decorative reservoir used for discharging water. It is also a structure that jets water into the air for a decorative or dramatic effect in landscapes.