A City Hall Virtual Tour TOUR OFFICE | COURTYARD | N. PORTAL | W. PORTAL | S. PORTAL | E. PORTAL | MAYOR'S RECEPTION RM. | CONVERSATION HALL | NE STAIRS | CAUCUS ROOM | SUPREME COURT | GRAND STAIR | LAW LIBRARY | TOWER | EXIT TOUR

he four corner pavilions of City Hall are dedicated to vertical movement and are little more than huge stairtowers. Despite the fact that Elisha Otis demonstrated his elevator as early as 1853, it did not become a factor in the new City Hall plans until midway through the construction. Consequently, the stair was a very important design element. McArthur's design called for four enormous spiral stairs to rise up 120 feet from the ground floor to the sixth floor in each corner of his building.

onstructed of granite, the octagonal 'flying staircases' are considered to be one of the building's major engineering accomplishments. Looking up, you are immediately struck with the lightness, yet solidity of the stair. Polished granite lines the underside, and a sturdy bronze railing wraps around in a dizzing spiral opposite a polished granite wainscot. The granite landings and steps extend a full seven feet from the wall without any visible means of support!

ow these 'hanging | floating | flying ' stairs remain in place has confounded many people through the years. It was a particular problem for City engineers who were given the difficult task of replacing a section of the southwest stairtower that was damaged in a 1956 fire.

fter six months of study and probing, the answers were discovered. The stairs rest on a solid rock foundation built up from the basement. Each stair and landing is inset 14 inches into the wall in a cast iron box. The steps and landings are then keyed together to form what is known as a spiral arch - a sound engineering concept where each individual component helps to support the whole.

espite the soundness of the theory, looking at this magnificent structure still has to make you wonder how it is able to defy the laws of gravity.

e will exit the stairtower at the fourth floor and once again walk north to take a peek at the other half of Conversation Hall, the room now used as the COUNCIL CAUCUS ROOM.