Originally the ceiling was to be a skylight, but funds ran out and Paul Helleu was commissioned to paint the night sky on the vaulted ceiling. He conceived of the constellations, complete with the zodiac signs. He took the imagery from a Medieval manuscript. Centuries before, travelers looked to the stars in order to find their traveling path. When Grand Central Station was built, trains and railroads replaced the need to travel by the stars. The constellations, however, remain fixed on the ceiling of Grand Central; they remind travelers of the way things were and the progress that has come. Despite the fact that there were multiple astronomers involved, somehow the actual depiction of the celestial sky was not very accurate, a fact pointed out shortly after it was installed. By the 20's the roof had begun to leak. The mural faded and was covered by soot. By 1944 it had been covered by a cement and asbestos hung ceiling. When the terminal was restored in 1998, the asbestos ceiling had to be carefully removed and the original ceiling was carefully restored.