The train is the recommended way to explore Europe in a relaxed manner. There are many reasons to prefer trains over planes, cars and buses for travel in Europe. To name but a few:
A dense network: nearly every city has one or more stations which are served by trains multiple times each day.
Many have commented that the best part of train travel is the great location of the stations. Major stations are usually located in the center of the city. Shops, restaurants, hotels and public transportation are all only a few steps away. You don’t have to pay high taxi fees or wait for a bus to bring you to your hotel.
Another major advantage : checking-in means simply getting on the train. You check the timetable for a train that you find convenient and then get on board at that time. It is just that simple. There are no long check-in lines and you don’t remove your shoes and belt or walk through a metal detector. You can bring your own food and drinks or buy them on board the train. Especially with a Eurail Pass you can hop on and off trains whenever you feel like it. The only limitation is the advance reservation that some popular trains require.
A free benefit of train travel is the great view from the train window. You see more than just clouds or ugly gray sound walls, much more than the dirty back of a semi-truck. You experience the beauty of Europe. From the train you see the lush green hills, the colorful cities and the quaint countryside. Unless you travel overnight...
The environmentally concerned will take heart in knowing that they are using comfortable, affordable, mass transportation. Trains are relatively eco-friendly in relation to global warming. The Time Out guide Flight-free Europe gives an example: "A passenger on a Eurostar train from London St. Pancras International to Paris Gare du Nord produces about 5.5kg of carbon dioxide; the same person on a flight from London Heathrow airport to Paris Charles de Gaulle would produce 60kg."
Border controls are limited in a large part of Europe. In 1985, the Schengen Agreement (see Wikipedia) was signed by Germany, France and the Benelux countries. Several years later more European nations joined this agreement. Rail passengers no longer have their identity checked by border guards when crossing borders of the Schengen countries (however, security controls by carriers are still permissible).
As more countries join the European Union the more freedom of travel you get to enjoy as a visitor. When using the Eurail Pass you won't be waiting in long lines at security check-ins, you get the freedom to explore cities of your choice at your own pace. See Europe using the most modern, safest, low cost means of transport possible, the train.