This is an oil painting by the French painter Maurice Denis (1870-1943). I was unsure of its authenticity so I contacted Fabienne Stahl, an authority on his works and responsible for the compilation of the Catalogue Raisonné de L’oeuvre de Maurice Denis.
Apparently the painting had not been seen previously by her but she was able to confirm its authenticity and to date the painting to 1905 based on a sketch “Porte des Grenades” in the their collection.
Checking online I discovered a recent photo of the Porte des Grenades and am amazed that the painter’s viewpoint holds true.
Here is some further information about the artist: Maurice Denis attended the Académie Julian with Paul Sérusier and Pierre Bonnard, who had shared ideas about painting. Through Bonnard he met additional artists, including Édouard Vuillard, Paul Ranson, Ker-Xavier Roussel and Hermann-Paul. In 1890 they formed a group which they called the Nabis, taken from “Nabi”—Hebrew for “Prophet”. Their philosophy was based upon the philosophy of positivism. Denis described it in 1909: “Art is no longer a visual sensation that we gather, like a photograph, as it were, of nature. No, it is a creation of our spirit, for which nature is only the occasion.”