Lower Saxony  (German: Niedersachsen [ˈniːdərˌzaksən]) is a federal state (Bundesland, plural Bundesländer) in northwestern Germany. It is the second largest state by area (47,618 km²) and fourth largest by population (nearly eight million) among the country's sixteen states.
There is a special ticket called the "Niedersachsen Ticket"  which offers unlimited travel by regional trains inside Lower Saxony area, up to Bremen and Hamburg in one day. This ticket is not valid in high speed trains (D, EC, IC, ICE) so make sure you board the right trains (RE, RB, S-Bahn, Metronom) when using this ticket. It is valid from 9am to 3am the following day during weekdays and the whole day on weekends. There are two types of tickets, the group ticket (up to 5 people, €28) and the single ticket (€20). These tickets are also valid inside public transport network in some of the cities (Hanover, Hamburg, Bremen, Brunswick).