Choose Advanced Search. From the drop-down menu on the left, change Any Field to the Subject field.
The subject heading for maps is, you guessed it, "maps." You can do a subject search in QuickSearch such as:
Tanzania -- maps
to find maps at Rutgers University Libraries.
Alternately, in Advanced Search, you can select Maps under the Resource Type limit on the right.
You will also want to search for maps found in books. A book containing maps will almost always have a note in the catalog record that says, "illus."
Therefore, an Advanced Search such as:
subject= Tanzania AND Any Field = illus
will give us results such as these, all of which certainly contain maps:
Historical dictionary of Tanzania / by Laura S. Kurtz. Metuchen, N.J. : Scarecrow Press, 1978.
Ecology and change: rural modernization in an African community / by C. Gregory Knight. New York, Academic Press [1974]
The geology of Kilimanjaro: [the results of the Joint Sheffield University-Tanzania Geological Survey Expeditions in 1953 and 1957]
Tanzania, a profile. New York, Praeger [1972]