Street level subway entrance

Before starting on another big project I thought I'd work on a few smaller ones. I started with making repairs to a number of buildings, and then thought I'd have a go at building a street level subway entrance.

There's all sorts of stuff on Toronto's streets that I'll need to include to give a you-are-there-sense to things, but a street level subway entrance is something I've been meaning to try for awhile. 

No, there isn't going to be a subway on the layout, but I thought I needed an entrance to suggest that there's one. It's basically going to be a styrene box that will be inserted into a hole in the sidewalk. It might need a light, and maybe a mirror on the underground end; however, I started with the stairs. They're made from 20, 6' wide strips of 0.080" x 0.25" styrene. Next step: figuring out the dimensions of the surrounding entry and building it up from styrene sheets.