Roger Zelazny published a simple map
of Amber and the nearby areas
(Mt. Kolvir; Garnath; the stairs to Rebma)
as part of the original serialization
in Galaxy magazine.
The map appeared in Galaxy,
Volume 39, No. 2, pg. 101.
Thanks to one of the members
of the Amber email list,
I've gotten a copy of this map.
Here it is.