In Greek myth, before the pure souls could enter the Elysium Fields, they would first come to a grove of black poplars and sterile willows. This was the Grove of Persephone. Here, the souls would meet with Hades and his wife Persephone.
In God of War: Chains of Olympus
In God of War: Chains of Olympus, the groves lie beyond the Temple of Persephone. In search of his daughter, Kratos enters the grove after traversing the temple. There, he finds Persephone, who tricks him into draining all of his power into the Forsaken Tree in order for him to enter the Elysium Fields. There is a portal to Elysium within the groves, as well as the tree.