Garden of Eden
God loved them so. His prize creations, until He banished them and all of mankind from the perfection of the Garden. And He hid it away.
When God created the world, He created the Garden of Eden, the crossroads between divinity and humanity, where he kept His prize creations, Adam and Eve. However, Gadreel, the angel who was tasked to guard Eden and prevent any evil from entering, allowed Lucifer to enter the Garden. The archangel's actions led to the corruption of humanity and their exile from the Garden. The Garden of Eden was hidden away, and appears to exist in an alternate realm outside reality. According to Castiel, no one has been there since the exile of humanity, however the Garden can be accessed if a non-human entity consumes the Occultum.
Within the Garden is a young girl and an albino python snake. The young girl appears to have great knowledge of the Garden, but her actual purpose is not known. The snake or the nature of the Garden itself appears to have the ability to restore lost souls in soulless people.
When Metatron uncovers "Ezekiel's" real identity, he reveals that Gadreel was the angel who was tasked to guard the Garden of Eden to prevent any evil from entering. Castiel explained that he was the angel who allowed Lucifer into the Garden, which led to the corruption of humankind, the creation of demons and Hell, the departure of God, and the archangels' scheme to start the Apocalypse. Gadreel's actions led to his eternal imprisonment in Heaven's darkest dungeon until he was released as a result of the Fall. However, when Gadreel tries to explain, he told Dean he loved humanity and set them free, but he is adamant that what happened in the Garden wasn't his doing. Sam feels that while he was possessed, he believed that Gadreel felt misunderstood.
When Jack consumed the Occultum, he was sent to the Garden of Eden where he was greeted by a little girl who explains the history of the Garden. When Jack asked her about how the Garden was supposed to change him, she tells him that the Garden will change him if he's "the one meant to find it." When she leaves, a snake appears from a tree and asks Jack who he is and who he is meant to be. Suddenly, Jack gets flashbacks of his memories, both good and bad and collapses on the ground in tears. Jack is sent back to the church where the Occultum was hidden as ball of light, killing a pair of hellhounds upon his return.
Eden in Lore
The Garden of Eden was believed to have been created by God when the world was created as a paradise for humanity. However, when the serpent tempted Adam and Eve to eat from the Forbidden Fruit from the Tree of Knowledge of Good and Evil, they were banished by the archangel Chamael and two cherubs with flaming swords were sent to protect the Garden. The Garden's location is believed to be located in Göbekli Tepe, an archaeological site in the Anatolian Region in modern-day Turkey.