Mountains of maps? (5)
I believe the answer is:
atlas
I believe this is a double definition.
'mountains' is the first definition.
(I've seen this before)
'maps?' is the second definition.
(printed collection of maps)
'of' acts as a link.
(Other definitions for atlas that I've seen before include "In Greek myth, a Titan made to support the heavens" , "One of the Titans" , "book of world records?" , "Chart book" , "Asian satin" .)