, and the minute hands are long. The clock has Westminster Chimes, which sound on the quarter-hour, and can be heard from the Queen St Mall and, at times, in the surrounding suburbs. The time keeping is controlled by a master clock imported from England. The dials, hands and slave mechanisms were designed and built in Brisbane by Synchonome. Above the clocks is an observation platform, open to the public and accessible by lift between 10:15 am and 4:45 pm seven days a week, free. For many years this afforded extensive views of Brisbane, but since the relaxation of height limits for surrounding buildings in the late 1960s, the view is now somewhat restricted. Auditorium The centre of City Hall features an auditorium, based on the Pantheon, Rome, and several smaller reception rooms. The auditorium is a large circular hall that can seat up to 1,600 people and is covered by the largest copper dome in the southern hemisphere. Beneath this dome there are 8,500 L.E.D lights that display a light show. When originally built it was intended that the building would house most of the council's administrative offices, Aldermen's (councillors') offices, the Council Chamber, a public library and several reception rooms, in addition to the auditorium. As the role of local government increased in the 1950s and 1960s, the reception rooms, hallways and side entrance vestibules (in Adelaide and Ann Streets) were converted to office space. Additional offices were constructed on the roof and in the basement. Construction material The building is constructed of concrete, brick and steel, with a base of Camp Mountain Granite. The granite was extracted by the first builder, Arthur Midson, from his quarry at Camp Mountain near Samford. This deposit was worked just for the City Hall project. Above Midson's granite base courses, the east, north and west sides are clad in Helidon freestone, a type of sandstone extracted from Wright's Quarry at Helidon. The sandstone cladding was constructed (together with the rest of the building) by builder Douglas Dunn Carrick. The clock tower has a steel framework, and is clad in the same sandstone. The interior includes four marble columns, two of which support an arch above a ground marble staircase. Granite for the ground floor and basement was sourced from Enoggera. Sculptures Pediment The sculptured pediment above the portico and entrance, known as the tympanum, was carved by Brisbane sculptor Daphne Mayo