After World War II many European cities were severely damaged and in need of urban renewal. London and other British cities which had suffered the Blitz were pock-marked with bombsites, vacant lots covered in the rubble of destroyed buildings. Postwar children in urban areas share a common memory of playing their games and riding their bicycles across these desolate environments. There were often abandoned bombshelters nearby with "keep out" signs on the front.
In London, Liverpool, Bristol, etc. and across the channel in Berlin and other places these sites were constant reminders of the death and destruction of the war. This was a contributory factor to the European psycho-sociological outlook of the 1950s and 1960s.