Community Gardens of New York City.

Some of New York City's community gardens have been around nearly 30 years. They're stunningly verdant, in the midst of skyscrapers and sidewalks, with the sound of cars and sirens clanging around between the buildings. Within the gates of the gardens you're embraced by the misty, fragrant atmosphere of a forest, and can safely peer out between the bars at the buzzing jungle of the metropolis on the other side. The juxtaposition is enough to make you dizzy.
Both of these images are from Liz Christy Garden, one of the first projects of the Green Guerillas. The shiny building behind the greenery is brand new. The developers were planning to destroy the garden, but the Guerillas and gardeners resisted successfully.