It seems each major city in US has at least one area that is drug infested and pretty risky.
In Orlando Florida area, an area behind downtown police building is one such area. I will not venture into that area even during day time alone and there's no way I'd go there during night. It's kind of scary because it's right next to very popular convention/trade show/concert complex. If you don't know the area and make a wrong turn, you'll be in it before you realize it.
If you are planning to go anywhere, it will be wise to ask someone local if and where those places exist, especially if you intend to go on foot and with an expensive looking camera.