No one really knows where Eden is! Some think it was perhaps located in the marsh lands of Mesopotamia, modern day Iraq, because of the general location and the ancient name for the region being somewhat close to "Eden". But because of the flood and the change over time, I think it's impossible to verify.
Broadly speaking, any history before 3000 BC gets pretty fuzzy and is subject to a great deal of interpretation. There are many historical places in the Bible that are unknown to us, such as where the Tower of Babylon was, where the Hebrews crossed the Red Sea, where Mount Sinai is - or even later questions such as where Jesus was buried etc. Though there exist many compelling theories and a lot of tradition to give us some ideas.
Nod and the City of Enoch - I'm sure there are many theories, but I'd be inclined to guess some place in Mesopotamia because that's where the first cities that we know of started to appear. In Abraham's day, Ur, Uruk, Akkad, City of Babylon, Mari, Assur and Nineveh were notably established and unlike any place on the earth. If this is where civilisation started after the flood, it could make sense to trace it back to even earlier cities, like Nod and Enoch; especially if Eden and Babylon was in this region - though we don't know. Furthermore, who knows what the world was like before the flood.
In any case, I believe God intended it this way. If we knew exactly where Eden was, I think a lot of people would obsess over the area and it would inevitably become a "holy site" which would distract from the Gospel. What's important is that we have a firm promise of a new Eden through our Lord Jesus Christ!
