I'll limit this to existing Amtrak trains. Is there a section of a route you could ride over at one time but has been taken out of service more or less permanently? I'm thinking of: the Phoenix AZ segment of the SUNSET LIMITED. the Dallas-Ft. Worth segment of the TEXAS EAGLE on the T&P/UP. the Auburn-Pasco segment of the early EMPIRE BUILDER. the section of the CITY OF NEW ORLEANS in Mississippi re-routed onto a different IC line.