Atop the wall, largely hidden from view here at street level, is the Long Island Rail Road's Richmond Hill yard. Within the yard is a car wash facility — one of three in the LIRR system — for bi-level rail cars. The two green-roofed structures in this aerial view of the yard are car wash sheds. The structure above, which can be found in the upper right portion of that aerial view, is only a few years old (it was under construction in 2013), and it appears to have some car-washing function as well: if you zoom in on the gray box near the middle of the photo, you'll see two labels reading "HIGH PRESSURE HOT WATER" and "HEATED DETERGENT". Looking again at the aforementioned aerial view, you can see that this structure straddles a track; perhaps it's designed to allow people to walk around the elevated platform and manually wash a rail car sitting beneath it.
Just to the west of the car wash is the adjacent Morris Park yard. Looking at an aerial view of Morris Park, you can see a roundhouse and its turntable — apparently the LIRR's last active turntable.