This is the "A Valley" by Philippe Rousseau, painted in about 1860.
Rousseau is best known now as a still-life painter, but early in his career he painted landscapes in places like Normandy and Brittany. This painting dates from later in his life, when he was already established as a still-life artist. The view is along a sunlit valley under a bright sky.
While the exact location of this valley can't be pinpointed, the hillside at the left with its small fields or kitchen gardens is reminiscent of Pissarro's views of the same period, painted around Pontoise to the north-west of Paris. You'll notice rows of vegetables and what looks like poppies on one strip.
The fresh cool tone of the greens and the loose brushwork are actually quite different from many landscapes painted by artists of the Barbizon School at that time. This technique is more comparable to early Impressionist paintings, with a high horizon line which was also used by Millet and Corot in their own work.
A Valley hangs in The National Gallery on Trafalgar Square, London — free to enter. Point your phone at any artwork there and audioguide.london plays a free audio guide in six languages — no app download needed.