Philadelphia City Hall Interiors

The building contains four sets of cantilevered stairways, each containing 156 steps.
"A technological marvel, each flight is fashioned from a single, self-supporting granite slab."

A view of the wall below the tower near the elevator entrance.
The guide told us that Philadelphia started their own brick company
so that they could get bricks that were much denser and heavier than normal industrial grade bricks.