The phrase "concrete jungle" refers to an urban environment that is filled with tall buildings, roads, and lots of human activity, symbolizing the lack of nature and natural surroundings. Full definition
It is concrete jungle full of people's energy and creativity bouncing off of those beautiful solid buildings. (stylebythepeople.com)
The main feature is the bespoke floral embroidery on the sleeve and hood that conjures up images of botanical gardens and the rural countryside — even though in reality, you might be stuck in concrete jungle — a.k.a. the city. (jackwills.com)
Although I still maintain that squirrels are at the top of the animal kingdom in the urban concrete jungles of NYC. (nystateofpolitics.com)