City of Greyhawk Contour Map
Please forgive the grade-school style of my work, but I've never been a dab hand at drawing or cartography.
This map is based on the map found in Gygax's City of Hawk's novel.
The Purple is the highest elevation with each color depicting around a 50 foot rise, then descending red, green, and uncolored. The Blue represents the Selintan River. The red lines represents the city walls.
I placed the Citadel at the highest elevation. High, Garden and River quarters I envisioned as hills that had been shaped and plateaued. The University and Clerkberg areas as well. The Old City I saw as a two step plateau with a higher elevation in the center with one end containing the old city barracks, now the prison workhouse.
For the most part I have seen the City of Greyhawk depicted as flat, but in City of Hawks it mentions that, "The rambling walls follow the entire complex of ridges and hills that rolled from the northern tip of Old City to where the Grey Run and the Selintan flowed together."
The colored splotches shown on this map are a very rough estimate. Within each area I see winding streets, some clif-like areas while others rise slowly to higher areas. Some areas may have a more ridged or sculpted appearance, while many of the streets and buildings may tilt at angles in a ramshackle and shoddy construction.