This sample shows how to use ZoomLevels to control what layers are drawn on the map.  In this example we start out with the map zoomed out to show the entire world.  When we are at this extent we show all of the countries and the states within the United States, but as you zoom in closer towards Austin you will see that the major interstate highways will begin to display inside the United States.  If you continue to zoom even closer towards Austin you will see the counties of Texas displayed as well as the city streets of Austin. 

ZoomLevel work great for only showing the necessary information for a certain zoom level.  For example you wouldn't want to see all of the street data when the map is zoomed all the way out to cover the entire world because the map would be unreadable.  So to prevent this from happening we setup a ZoomLevel to only show street level detail at a zoom level of 50 miles and lower.

To try this sample app out, click the track zoom icon on the far left of the toolbar and draw a track rectangle over the mid portion of the United States.  Then continue to zoom in towards Austin and you will see that other layers start to appear.