GapVis is a free tool developed in conjunction with Google Ancient Places to visualize the locations within and allow the exploration of books referencing ancient places within the Google Books collection. Users can view text summaries, use an enhanced reading interface and explore the location references through a place detail view. It is intended both to enable location-based text discovery, and to allow users to delve more deeply into a text based on the locations referenced within it. GapVis is currently in beta.