Our Main Stairs

I was recently talking to someone about opening our skylight a few years ago. We were talking about the staircase, and how unusual it is, and how the stairs work with the skylight. 
The stairs are grey marble, which was probably locally quarried, perhaps in one of Baltimore County’s well-known quarries. I have the builder’s specs somewhere, and the actual marble is specified in there. I know the outside stonework is. 
We are fortunate to have a copy of the original blueprints, and on them, you can see the staircase clearly, and the genius of the architects, Ellicott & Emmart. 
On the ground floor, with the center hallway with its tesserae marble floor and beautiful wood trimwork, the staircase is wide and sweeping. 
As you rise up through the floors, the stairs narrow and the opening between the sides widens. This effectively funnels the light down through the staircase so that each set of stairs is well-lit. When you get to the set leading from the ground floor to the basement, there is no space between them. Once we re-opened the skylight, the true intent of the architects became apparent.
Each set of stairs is actually three sets, intersected with two landings, as you can see in the image above. From the basement to the third floor, the stairs are Calacatta marble in grey and white pattern. The landings are one-inch by one-inch marble tessarae tiles, surrounded by black marble. 

From the basement, to the top of the fourth floor, the railings have a classically elegant ironwork in an oval and ball pattern. You can see it behind another hunk of marble!
When I walk down from the third floor to the basement kitchen, I always count the steps, and there are 78 of them. I think that there are probably another 20 steps up to the top floor.