The map you're looking at is place names extracted from the Project Gutenberg version of Thucydides's History of the Peloponnesian War and compared against the US NGA's GNS.

The places shown are selected from the database with preference given to those mentioned more frequently in the history. Try clicking on the map to pan around, and zooming in and out to see different places relevant to Thucydides's account of the war. At each zoom level, the places mentioned most often in the book are shown. Obviously, some places are missing; others are false positives. Future work on this project will include a wiki with a page for each location, so that users can improve and annotate the auto-generated map.