Thank you for your responses.
The civil engineering department at ETH Zurich, doesn't require much additional documents except : A certificate for the German Language (which I have), the GRE General test (320), and Course content information. Not even Letters of recommendation are required, even though I have two of them from the professors of my hometown University which I am going to send (don't know how much they evaluate that though, since it is not required),2 years of work experience. But my average grade is rather low, just 78%.
But I don't know, their response via Email sounded very strict to me.
Thank you guys, for responding and sharing your personal experiences, it really helps.