Google Maps (maps.google.com) is a very good site for planning a trip. You can type in the name of a point of interest (e.g., empire state building), and it will pin the location on a map. The map includes a graphic scale at the lower right corner.

If you enter another point of interest (e.g., new york public library), the first pin disappears and a pin for the new point of interest is displayed.

Is there a way to get Google Maps to not hide the first pin? I would like to enter several locations, and be able to see where they all are in relation to each other.