According to its title, Brueghel's painting is meant to portray the Fall of Icarus. It shows Icarus' legs splashing into the water as his wings fail. As the title also implies, it shows a landscape, seemingly just to give a setting for the fall.
Auden's poem references specific details from this painting, but does so with the intention of pointing out how people, too often, ignore other human suffering. Her poem focuses on the bystanders in the painting, and how they are all turned away from Icarus as he experiences this tragedy.