Concrete Jungle Meaning

(idiomatic) An urban or other populated area containing a high density of buildings constructed of concrete or similar materials, especially one which lacks greenery and which seems unattractive, harsh, or unsafe.

Example: 1948 9 April, Richard Coe, “Hellinger Mixed Real Manhattan”, Washington Post, page 24:
  There is nothing quite like the affection of a transplanted New Yorker for his native concrete jungle.
2007 29 October, “Spain aims to restore overdeveloped coastlines to a more natural look”[1], International Herald Tribune:
  Spain plans to restore a fifth of its coastline from overdeveloped concrete jungle to a more natural state.