Who owns wall, that house is built on top?

Ok, I have 2 duplexes next to each other, that are sitting way up - 20-25’ - just guessing. The retaining wall, facing a major street, was built by the city.
I think the wall would run along my property line.

Who would own the wall? Would it be like a utility easement and that I own and maintain, but they can do something with it, when they need to?

On top of the wall is a 6 fence, that encloses the property.

I’m just thinking of potential for a billboard in the future. There’s some major retail development happening across the street in a few years and it would probably be nice to have extra income by renting advertising space.