Quote taken from Source:
This is my latest and most ambitious digital painting of a Chicago scene unveiled at Photoshop World in Miami on March 22, 2006.
It is a panorama of the Damen Station on the Blue Line of the Chicago Transit Authority.
Adobe Illustrator was used for generating the majority of the basic shapes as well as all the buildings in the Chicago skyline.
The rest was created in Photoshop.
• The image size is 40 inches by 120 inches.
• The flattened file weighs in at 1.7 Gigabytes.
• It took eleven months (close to 2,000 hours) to create.
• The painting is comprised of close to fifty individual Photoshop files.
• Taking a cumulative total of all the files, the overall image contains over 15,000 layers.
• Over 500 alpha channels were used for various effects.
• Over 250,000 paths make up the multitude of shapes throughout the scene.
Original Site here