Treasure maps can be found throughout Tamriel and they are used, of course, for finding and looting treasure chests. You need to have the very map in your inventory for the chest to appear and to be able to open it.
The level of the items inside are adjusted to the level of the zone (depending on what alliance you are playing).
Treasure maps are usually found on dead NPC's that you have killed or in chests.

 

 

PRESS PICTURE TO OPEN