 The Marble Hall is the basement of Mt . St. Peter 's and is 125 by 55 feet ( 38 by 17 m ) . Before the church had been completed , this area had been filled with valuable material from the Mellon Mansion until the materials found their proper places in the upstairs of the church . By winter of 1944 , the basement was completely empty . During this time , there were men working on building the Rectory , but since there was much snow , they could not return to their work on the Rectory until spring . Nicholas Givens had donated a large quantity of marble for the basement , so they began work on the basement . The workers covered the ground with black asphalt tile and the walls and pillars with white Carrara marble . Two marble altars were constructed along with a large kitchen built to feed up to 400 people . They also built a furnace room and a large workshop to the side of the kitchen . 
