If you ever wanted to visit every interesting historical site in the U.S., a map created by University of Waterloo professor William Cook and his team of researchers, will guide you on a tour to each one using the mathematically shortest route possible.
It uses Google Maps to figure out the shortest route to see every single site listed on the U.S. National Register of Historic Places. It may take you a while to visit each site, however. The shortest possible route covers 217,605 miles—or somewhere between eight and nine laps around the equator.
Check it out at http://www.math.uwaterloo.ca/tsp/us/tour.html.