Guggenheim New York — New York, NY, USA

This was painted not long after he started teaching at the Bauhaus, and it's often pointed to as the moment his early, looser abstraction gave way to these harder, more measured shapes he'd keep using for years after.

From what I can find, he limited himself to one shape here on purpose, just to see what color and scale alone could do without any other form to lean on. He apparently believed the circle was the most spiritual shape a painter could use.