€30 fixed price, plus booking fee for some sales channels. Availability is limited, which means that pass holder seats will be sold out before the train is full.

Yes you can, as long as the trains you use are included. In Spain, all cercanías run by RENFE are included. However, in Paris, the RER trains are not included. The TER trains are included. Metro is never included. In London, the Overground, the Elizabeth line and Thameslink are included.

In many of these cities for those not used to the systems it may turn out to be very complicated to work out what is included or what not. In fact several RER=local trains around Paris lines are included in pass-at the counter they will give you a ´contremarque’to pass the gates. F.e. to Fontainebleau-a major tourist draw. But sometimes it may even be that some trains on that line are included and others not.

In many german cities (not very populair with most passusers) there are S-bahn networks that also do urban travel, these can be used-some are not done by DB anymore.

They did so 20 years ago but currently, RER is not included.