Thanks to an extensive rail network with trains running at a good frequency, a trip to Graubünden can be done without even a car-unless you insist on traveling up every tiny valley. A Swiss Pass gives you access to all trains and buses (supplemented at times by the Apline Pass). A FlexiPass can be used if you intend to use the trains only on certain days.
Swiss Federal Railway (SBB/CFF/FFS. 0900/300300. www.rail.ch).