Hi Samy, if you are planning a trip to europe by train, be sure to check out the following link:
http://www.interrailnet.com/
The inter-rail system exists for many years and offers amazing prices for train trips all over Europe. The idea is simple: Europe is divided into several zones, you can buy an unlimited ticket (by km that is, the ticket is valid for 1 or 2 months if I'm not wrong) for 1 zone or for more than one. This way you can travel easily without the hassle of buying tickets every time and with the freedom to change your route without having to pay extra money.
Have fun, Hope I helped in something...
Adebisi (Nickname), ITALY