Writing a city

Writing question: I'm playing with a plot, and while I have a loose idea for a city to set it in, I'm having trouble picturing details. And, I mean, I can leave it vague; that's usually how I roll when it comes to settings. But if I wanted to get a sense of the layout / population / amenities of a city from a historical period, are there good (easily accessible) resources for that kind of thing?

( Some details of what I know and what I want to know. )

Any leads would be greatly appreciated!