sentences:  Some of the most significant design elements of the building include the Grand Lobby, which is a naturally lit atrium with a 47-foot high barrel-vaulted ceiling.The ceiling is held up by bronze columns crafted by Louis Tiffany Studios.They feature at their bases, the Seals of Pittsburgh and Allegheny County, frontiersman Guyasuta, and Pittsburgh's oldest surviving building, the Fort Pitt Blockhouse.