Haven, the Free City by Gamelords, Ltd. It was an urban setting for a DnD clone where everyone basically played different flavors of thieves. Since you were thieves, the game focused on personal interactions, intrigue, and political and social plotting in a way that was decades ahead of its time.
Tragically, the team behind Gamelords lost their main artist and a central content creator to a car accident in the early eighties, and the IP has languished in the basement of an acquisitive dilettante since 1986.
I recall this one, from LONG ago!
I've run probably a half dozen games of various lengths in the setting, which I love. Never used the game system provided, though I did use some of the agnostic systems included in the material for specific situations (a horse race, for example).
I've run it using everything from Dangerous Journeys to BESM to DnD to Dungeon World. It's a crying shame it's unavailable and unfinished, because it's a great urban/intrigue sandbox.
Gah! Anywhere legal to find this?
Unfortunately, a guy from Chaosium personally (not on behalf of the company) bought all the stuff up in 1986 and didn't do anything with any of it. (There were a couple sourcebooks for Haven – two out of the four planned – and then 10 magazine-style publications for their "Thieve's Guild" RPG that had a bunch of incidental stuff for the setting as well).
I've got hard-copies of all of it, and spoke with the IP owner a couple times about buying up the rights, but his asking price circa 1993 was ridiculous – basically wanted someone to buy up all his thousands of copies of stock at the retail prices before he'd talk about selling the IP.
Actually, it looks like the guy who bought up all the hard-copies of the game set up a website where you can order his stock. http://diffworlds.com/haven.htm
I can recommend Haven and Haven 2 especially. Everything else is fine, but less focused on the city itself.