Intercity-Express trains are, quite simply, the best way to travel between most German cities. Even on long stretches, such as Berlin to Basel, train travel is competitive with flying after you've factored in ground transportation and other hassles.
ICE trains run on principal business rail routes within Germany with hubs in Berlin, Cologne, Düsseldorf, Frankfurt, Hamburg, Hannover, Munich and Stuttgart. If you plan to explore neighbouring countries you can take an international ICE train to Austria (Vienna, Innsbruck), Belgium (Brussels, Liège), Denmark (Copenhagen, Arhus), France (Paris), the Netherlands (Arnhem, Utrecht, Amsterdam) and Switzerland (Zürich, Interlaken).
All ICE services offer First and Standard Class seating and over 90% of these trains have an on-board restaurant. Air conditioning comes as standard, seats in both classes recline and there is plenty of space for luggage. ICEs have power sockets in both classes around seats with tables and in recent models between each pair of seats. There is free wifi on board ICE trains in both First and Standard Class.
Reservations on regular ICE high-speed trains are optional. Reservations are compulsory on the ICE from Frankfurt to Paris, Munich to Paris, and Stuttgart to Paris.