Unknown photographer, Aerial of destroyed Frankfurt old town in June 1945, after heavy Allied bombing raids (die Altstadt von Frankfurt nach den schweren Bombardements durch Alliierte, Luftbild von Juni 1945). Source: University of Wisconsin via Wikimedia Commons, https://commons.wikimedia.org/wiki/File:Frankfurt_1945_June_destructions_after_bombing_raids_old_town_aerial.JPG. Public domain.