The most notable feature of the Main Concourse is the great astronomical mural, from a design by the French painter Paul Helleu, painted in gold leaf on cerulean blue oil. Arching over the 80,000 square-foot Main Concourse, this extraordinary painting portrays the Mediterranean sky with October-to-March zodiac and 2,500 stars. The 60 largest stars mark the constellations and are illuminated with fiber optics, but used to be lit with 40-watt light bulbs that workers changed regularly by climbing above the ceiling and pulling the light bulbs out from above.
Soon after the Terminal opened, it was noted that the section of the zodiac depicted by the mural was backwards. For several decades lively controversy raged over why this was so. The actual reason is that Paul Helleu took his inspiration from a medieval manuscript, published in an era when painters and cartographers depicted the heavens as they would have been seen from outside the celestial sphere.
If you look carefully, you will see a patch of dark on the carefully-restored blue of the mural. This patch shows the color of the ceiling before restoration. It was left as a reminder of how much work was done.