Create a version of the event index that instead of displaying a text based list of events, it displays a map with markers for each event happening given the specified filters.

Collect all of the events that match the date range, and use their venue location information to parse into map data.
Render a google maps style map with markers for each event.
When you mouse over the event on the map, show info about the event(s). If they click on the event, take them to the event details, or the venue entity details.
Allow the user to move around the map, zoom in and out.
Size the map to best show all the events while zooming in logically.