This daring picture reveals the insignificance of man's activity against the magnificence of nature. Almost two thirds of the canvas is sky; most of the rest is ice, imposing on the viewer the full force of this bleak winter day. The sky, the ice, and the horses are still and silent, only the men--small, indistinct--are moving. They and the city behind them are overshadowed--figuratively and literally--by the hazy grandeur of the scene. It is even more breathtaking to see in person. The best art says something you couldn't say as well any other way. This picture achieves that ideal.

(More, and an alternative interpretation, here.)