"The Limetz Mill," Claude Monet, 1889.
Y'all know Monet.
At a glance this seems like the left part is just darkness, like an oddly exposed photo. But on closer examination, it's a mass of trees and foliage by the side of a pond, with the mill appearing, almost as an afterthought, in the background.
The odd choice of angle is typical of Impressionism, with its focus on light. Here we've got a view from the shady bank of the millpond (located in a village along the Seine river, west of Paris), looking out across the water. It has a sense of immediacy and naturalness...which makes it a great demonstration of Impressionist technique and style.
This may not be Monet's prettiest or most famous image, but it is a painting that successfully demonstrates what Impressionism was all about. Plus it wonderfully has that feel of a summer day, ducking in the shade and resting and looking out at the view. You can just barely make out a couple of people on the bridge. It's an intensely summer-y painting.
From a private collection.