Genesis 2: 8-14
8 Now the LORD God had planted a garden in the east, in Eden; and there he put the man he had formed.
9 And the LORD God made all kinds of trees grow out of the ground—trees that were pleasing to the eye and good for food. In the middle of the garden were the tree of life and the tree of the knowledge of good and evil.
10 A river watering the garden flowed from Eden; from there it was separated into four headwaters.
11 The name of the first is the Pishon; it winds through the entire land of Havilah, where there is gold.
12 (The gold of that land is good; aromatic resin and onyx are also there.)
13 The name of the second river is the Gihon; it winds through the entire land of Cush. 14 The name of the third river is the Tigris; it runs along the east side of Asshur. And the fourth river is the Euphrates.
(Hey, it's been a few days, but I've always said I'll pursue this project when I feel like.)
Hmm. Where the heck is this place? I got out my trusty Oxford Atlas and I determined the following: The Tigris and Euphrates do not have a common origin, although they do arise maybe 100 miles apart from each other in a mountainous region of what is today southern Turkey. That's a long way from where Adam and Eve are about to find themselves, I must say.
So are there two other rivers that flow from somewhere near there? Nope, just one, a small river that flows north into the Black Sea, through Ankara.
Cush, it turns out, is a name for Nubia, which as everyone knows is on the Nile. The Nile arises in central Africa, more than 2000 miles away. Nobody seems to know exactly where Havilah is, but apparently it's usually associated with southern Yemen, which sadly is lacking in rivers except for intermitten watercourses (called Wadis) which arise in the mountains just north of the coastal plain. So the Pishon is most mysterious.
Anyway, Eden, clearly, is nowhere. As it should be, I suppose. The Hebrews would have been familiar with the Tigris and Euphrates, and no doubt may have had the impression that they had a common origin. From the vantage point of far northern Syria, it might appear that they are flowing from the same point, although it would not appear that way from lands better known to the Hebrews further south. The Hebrews, as far as I know, had yet to see the Nile when this story was first told, but they would have heard of it. Of course the Nile flows in the opposite direction from the Tigris and Euphrates, but back then they had no way of knowing that. (They will find out the hard way later on, of course.) And they no doubt heard tales of some other distant land which they imagined was watered from the same source.
In other words, Eden lay at the center of an imagined earth. The people who told this tale knew only the lands that they wandered themselves, as herders; and they heard tales of distant lands from travelers. But they had no maps and no way of assembling those tales into a coherent picture of geography.
Curiously, there was a river in the region where the Hebrews lived at this time -- the Jordan -- which arises in Lebanon a good thousand miles from the Tigris and Euphrates but in the same general direction from that vantage point. One would think that the Jordan would be a good candidate to be the Pishon, but it isn't. Canaan was not watered from Eden, apparently. Perhaps this reflects the Hebrews' deep sense of physical exile, a recurring theme throughout the Torah.