The masterpiece of Monet is entitled Waterloo Bridge. Effect of Fog, from 1903.
In those years, Monet made several trips to London, and his room at the Savoy Hotel overlooked the Thames towards Waterloo Bridge. Monet painted this subject several times, studying the changes in light due to the fog, caused partly by factory fumes. In this painting, the fog is lavender in color, enveloping and engulfing the landscape to the extent that it appears to be the very material of the bridge. The two small, dark boats and the smokestacks in the background bear witness to the industrial revolution in which the city had a major role to play.
An interesting fact: Monet was so obsessed with fog that he painted more than one hundred canvases depicting Waterloo Bridge, Charing Cross Bridge and Westminster shrouded in fog!