Tekkonkinkreet is a 2006 feature-length Japanese anime film, directed by Michael Arias and animated by Studio 4°C, adapted from the three-volume seinen manga series of the same name by Taiyō Matsumoto.
The story takes place in the fictional Treasure Town and centers on a pair of orphaned street kids: the tough, canny Black and the childish, innocent White, together known as the Cats, as they deal with yakuza attempting to take over the city of Treasure Town.
These images were scanned by Audrey Kawasaki from the artbook of the same name. Beautiful nostalgic imagery and amazing attention to detail. More on her Livejournal site.
I don’t take the time to watch animation (other than what comes out of Pixar) but I was blown away by this film.
You can purchase Tekkon Kinkreet on Amazon. Via Wikipedia.