Claude Monet painted several series of paintings on particular subjects — like the haystack series, poplars, water lilies and the facade of the Rouen Cathedral — revisiting the same subject multiple times in different lighting and atmospheric conditions.
The first of these series was of the Gare Saint-Lazare, one the large railway terminals in Paris. He painted 12 paintings of the train shed interior, train yard and environs.
Much of his attention appeared to be on the clouds of steam from the locomotives, blending at times into the Paris sky.
Wikipedia has a convenient page devoted to the series, with images of all 12 paintings.