It's not too often I'm given to singing the praises of a TSR product but if you're interested in a map of Lankhmar try to get your mits on TSR's old Lankhmar City of Adventure. This was easily one of their finest releases.
It included a poster sized city map with greyed out blocks in the centre of large residential and commercial areas. These were filled in using a seperate booklet of carefully prepared blank geomorphs which the GM could complete to his or her own preferences and plop into place as desired.
This was such a good and well executed system (Kind of an expansion of the Maze neighbourhood idea from Thieves World if anyone remembers it) that I still use it occasionally in my own RQ game world if players visit one of its few large metropolises. It also tied in very carefully with Lieber's books and looked great! (I'm looking at it now and reliving some happy crusty old gamer memories...)