Jean-Baptiste Camille Corot: Waterfall at Terni
Corot was one of the major (non-Impressionist) landscape painters of 19th century France. His later work was to have significant influence on the Impressionists. There is a wealth of online material about Corot; some examples are at Wikipedia, the National Gallery of UK and the Artchive.
Painters visited Rome and the surrounding countryside to record the natural beauty of the scenery and its antique monuments. The Cascata delle Marmore combines both, having been engineered in the third century B.C. to divert the river Velino into the Nera, a tributary of the Tiber. Corot visited the waterfall in summer 1826, attaining a mastery of plein-air technique that is characterized by the candor, naturalism, and seemingly intuitive structure of this sketch. Corot did not exhibit such informal works, but he tried to infuse the paintings he began to show at the Salon the following year with the same vigorous sensibility. [Metropolitan Museum of Art]