Just inside the main lobby of City Hall, the soaring rotunda is dramatically encircled by a keystone-cantilevered marble staircase, one of the first of its kind in the country and a feat of engineering ingenuity. The staircase rises from the lobby to the second floor, where 10 Corinthian columns support the coffered dome and oculus above, recalling the Pantheon in Rome. The marble flooring and decorative iron balustrade add to the rotunda's grandeur.

In 1858, during a firework display in celebration of the laying of the Atlantic Cable, the dome caught fire and was severely damaged. Subsequently, the dome and cupola were rebuilt by architect Leopold Eidlitz. In 1912-1915, as part of a larger City Hall restoration project, architect Grosvenor Atterbury lowered the height of the dome, widened and redesigned the oculus, added a frieze of plaster rinceau ornament and a new balustrade based on John McComb's original drawings, and painted the dome.

Throughout history, the rotunda has been literally and figuratively the center of City Hall. It has provided a grand entry for the many people who have come to City Hall to attend ceremonies, celebrations, and even pay their respects to the deceased. In 1865, crowds climbed the central stairs to mourn the death of President Abraham Lincoln, who lay in state just outside the Governor's Room. Two decades later, President Ulysses S. Grant lay in state at the base of the grand staircase.

In 1976, the Landmark Preservation Commission designated the rotunda an interior landmark. In 1995, the rotunda chandeliers were restored. As part of the 2010-2015 City Hall Rehabilitation, the rosettes in the dome were stabilized and the entire rotunda repainted. Additionally, the rotunda was equipped with new life-safety systems, including smoke detectors, sprinklers, and fire alarms.