The Pentagon is an office building, but built like no other office building ever. The original specs for the Pentagon envisioned a return to a micro sized defense HQ after WW2 ended, like we had after all previous wars, so the Pentagon would mostly be vacant. Thus it would be available for other activities. The proposed other activity was archives storage. So the floors were built to hold twice the floor loading weight of a normal office building and the floors were connected by large ramps. The Ramps themselves are huge and occupy quite a bit of the interior of one side of the Pentagon. The Ramps had an important functional purpose. If the national capital needed to be evacuated, then trucks could drive up the ramps and load the archives at any floor and simply drive away. The ramps are easily large enough for two 4-6 wheel trucks to pass each other, but are not tall enough for 18 wheelers.
When I first arrived at the Pentagon back in the mid 90’s, there was still a fleet of electric carts that could use the ramps for utilities work inside the building to access any floor and any main corridor. There were dedicated carts for plumbers, electricians, Office supply and furniture delivery, etc. Even a cart just to carry replacement light bulbs. Today, all those carts are banned from entering the interior of the building but a few are still used in the underground highway system between the b and c ring on the first floor. Only the electric ambulance carts are permitted inside today. On rare occasions, a cart will be used to ferry ancient vets to a ceremony inside.
So, mostly the interior ramps are an unused artifact today. They connect the 2nd floor to the third. The second floor to the fourth, and the fourth to the fifth.
Thanks to the reconstruction, they no longer connect the second floor to the first floor. So, they are useless for their intended purpose. [I recently found the first floor ramp. It was hiding. I will spend some time later exploring it]
The reconstruction plan for the Pentagon intended to take out the ramps and reclaim that office space for a huge increase to office floor space. But something happened and that part of the plan did not get executed. So now the old ramps sit idle, unused even by most pedestrians. But kept highly polished by the teams of cleaning people.