(excerpt from website...)
The Mellon Arena is famous for its revolutionary architectural design which features the largest retractable, stainless steel dome roof in the world--170,000 total square feet and 2,950 tons of Pittsburgh steel. The roof, which has no interior supports, is divided radially into eight leaves and is supported by a huge cantilever arm that arches 260 feet. The Mellon Arena, which was featured in the 1995 film "Sudden Death" starring Jean Claude Van Damme, boasts a dome that is designed to open or close in just two minutes.

The size of the Mellon Arena floor is 200 feet x 85 feet (17,000 square feet) for hockey, and can be expanded to 250 feet x 120 feet (30,000 square feet) by pushing back the A-level seats.