London went through a phase of using concrete as a facing material for construction a few decades ago. It has not weathered well. The concrete now looks tired, drab and in need of a clean. In some places it is stained dramatically – dark patches showing the run off of rainwater and pollution.
This is a section of a high-rise block of apartments at the Barbican in London. Stained concrete balconies. I saw the patterning and then I saw the pine trees in silhouette.