The main body of the building is called the cella. The exterior walls of the cella on the long sides with the columns form majestic corridors. The shadows falling at certain times of the day on the walls and floors of the corridors are very beautiful. Another interesting feature connected with the corridors is what has come to be known as the “Greek Urn.” This is the figure cut in the sky by the columns and architrave at the ends of the long exterior corridors. The Greek Urn has been made famous in literature by the poet Keats in his “Ode to a Grecian Urn.” The only openings to the Parthenon are the two pairs of great bronze doors leading off the east and west porticos. These doors are the largest in America and probably are the largest bronze doors in the world. They can only be challenged as to size by the Congressional Library doors at Washington or by those of one of the old cathedrals in Florence, Italy, and they are slightly larger than either. The doors are twenty-four feet high, seven feet each wide, a foot thick, and weight seven and one-half tons each. There is no doubt that the front entrance to the Parthenon was through the eastern doors. If there were no documentary evidence to prove this, and there is an abundance, the fact that all of the twenty-two gods of the east pediment are major deities of the Greeks while only four of those on the west pediment are major (the remainder being personifications and minor deities) would be sufficient proof that the eastern end was the front of the building. Entering the Parthenon through the eastern doors, the visitor most likely would first note the division of the main body of the building, or cella, by a transverse wall into two rooms—the east room and the west room. The east room is known as the Naos or temple proper. It is ninety-eight feet long, sixty-three feet wide, and has a ceiling height of forty-three feet. The most striking feature of the Naos is the double row of Doric columns, twenty-three below and twenty-three above, with an architrave between. These form a colonnade surrounding the main floor on three sides. The lower units of the colonnade are three and three-quarter feet in diameter at the base and twenty-one feet high. Those of the upper tier are two and one-quarter feet in diameter and sixteen feet high. The columns on the long side of the colonnade form with the interior cella walls beautiful and impressive corridors. Another interesting feature is that the floor of the corridors is raised an inch and a half above the main floor of the Naos.