If you are designing a Civ2 scenario, you'll want to have historical maps on hand to aid in picking the civilizations, setting up borders and especially laying out where cities are. The final section includes suggestions for finding historical maps and information on the web, including some really good sites to visit. Your favorite bookstore is unlikely to have extremely accurate historical maps, but there are other resources there that may help. Many bookstores are very nice about letting you paw through their collections, particularly larger ones like Barnes and Nobles'. I tend to start at the bookstore because they make better coffee than I do, and have more comfortable chairs than the university.
Encyclopedias are quite similar in terms of their coverage.
While such sources are excellent for selecting a time period to work with, and are good for naming civilizations, they are less good for the kind of detail-oriented map making required by scenario designers. The World Atlas is also a good starting point for maps, historical information, and so on. As a second pass, one might try to find books on the specific time period of interest. If y ou visit your local bookstore, try the history and military history sections first. You may be surprised to find useful information in other areas too, however, in particular the World Travel section.