Take this german rail pass for example:
The German Rail Pass from Rail Europe gives you unlimited train travel from four to ten days
This pass gives you unlimited travel on the national rail network of Germany.
And the limitations:
The German Rail Pass is not valid for travel on DB Autozug (trains transporting cars), chartered trains, private steam trains, narrow-gauge railways and museum railways.
I know you can use the trains (and some without reservations) from one city to another, in central stations. But am I able to use it inside a single city, in an unlimited fashion? In all german cities? Or "national rail network" means only city to city? Where can I get more information?
More information from official bahn.de website: you can even have a printed version but it needs to be a consecutive days pass! How to calculate a day from an employee perspective and from official db bahn 2014 flyer.