In the second chapter of Genesis we read how God establishes a celestial garden in Eden and places man there to till and cultivate it. The motif of a once heavenly paradise is prevalent in the ancient world and was more than likely borrowed by the Israelites from the preceding cultures of Near East. Evidence of this is in the word eden itself, which is Sumerian in origin and to whom it meant “plain.” the Sumerians occupied the Tigris-Euphrates valley no later than 3000 BCE
The oldest parallel to the biblical image of Eden is a land called Dilmun, often identified with modern Bahrain. We are given details about this country from a number of Sumerian texts, including the Epic of Gilgamesh as well as Enki and Ninsikila/Ninhursaga. In these narratives we read how Dilmun is a place located “in the garden of the sun…at the mouth of the rivers”, where disease and pain are nonexistent, people do not grow old, and animals do not kill. In Gilgamesh Utnapishtim (the Babylonian Noah) is placed there after the flood to live forever. In other mythological inscriptions we read how the god Enki along with his wife were placed there to institute “a sinless age of complete happiness”:
That place was pure, that place was clean.
In Dilmun the raven croaked not.
The lion mangled not.
The wolf ravaged not the lambs…
There was no snake, there was no scorpion…
There was no fear, no terror,
Man had no rival.
The whole universe, the people in unison
To Enlil in one tongue gave praise. —Old Sumerian Poem 
However, the two do have their dissimilarities; Dilmun is also a city and originally lacked fresh water. And while both are connected to important rivers, the inscriptions describing Dilmun are probably referring to the Tigris and Euphrates where as Eden is at the head of four rivers.
The Hanging Gardens of Babylons
With Israel’s reputation of borrowing from the Babylonians, it is worth speculating as to whether the author was at all influenced by the Hanging Gardens of Babylon, often attributed to the great builder king Nebuchadnezzar II (605-562 BCE). As a Babylonian garden, it likely consisted of statues of lamassu – winged guardian spirits – which may be related to the cherubim Yahweh placed at the east of his garden to guard the tree of life. 
Also worth pondering over is a painted mural from the palace of King Zimri-Lime at Mari (1786 BCE), containing features which are easily associated with the Garden of Eden. Most significant are the two types of trees placed parallel in the center, with winged guardian creatures surrounding them. While more of a stretch, one could also identify the four streams of water emerging from the jars held by two figures at the lower half of the central panel with the four rivers that flow out of Eden.
These paradise parallels are quite significant, for even if the author of the second chapter of Genesis wasn’t directly influenced by the Sumerian Dilmun or the Hanging Gardens of Babylon (the latter being our best candidate), it at least shows that this motif was not unique to the Israelites but rather originated centuries before and persisted into the first millennium.
- Ancient Near Eastern texts describing Dilmun via ETCSL
- Wiki on Dilmun in mythology
- Book: Secret Origins of the Bible by Tim Callahan
- Book: Memories and Visions of Paradise by Richard Heinberg
- Book: The Harps that Once…: Sumerian Poetry in Translation by Thorkild Jacobsen
- Book: Before the Muses: An Anthology of Akkadian Literature by Benjamin R. Foster
 The Epic of Gilgamesh, Translated by N. K. Sandars (Revised. Penguin Classics, 1960), 21, 29.
 Enki and Ninsikila/Ninhursaga, 13-23, translated in Thorkild Jacobsen, The Harps That Once–: Sumerian Poetry in Translation (Yale University Press, 1997), 186
 Heinberg, 41
 Jeremy Black and Anthony Green, Gods, Demons and Symbols of Ancient Mesopotamia: An Illustrated Dictionary (First Edition. University of Texas Press, 1992), 23.