Gamma Forests

The Gamma Forests was a location of unknown origin. The girls from there were known as "Gamma Girls". It was also a location neutral from recruitment for the Church. The forests there were not known to have ponds, only rivers. The people there were know to craft handstitched "prayer leafs", a cloth gifts with the names of their children embroidered in their native tongue. The leaves were kept by the people there as a sigh of devotion in the belief the child would always come home to them.

When Lorna Bucket was a child she once met the Doctor there. She recalled that he repeatedly told her to "Run", implying the situation they faced together had been dangerous. She also implied the reason she enlisted was partly because the Doctor's short visit to the forests was the only thing that had ever happened there. Lorna later crafted and gifted a prayer leaf to Amy Pond, who had recently been seperated from her newborn daughter.

Later as Lorna died, the Doctor pretended to recall their adventure there, despite the fact he did not recall Lorna. It is possible the incident has not yet occured for the Doctor.

After Lorna's death, River Song appears and mentions the Gamma Forests in part of her argument that some of the horrors he faces now is a result of what he has become. That the kidnapping and use of newborn Melody Pond as a weapon against him is a result of the fear he elicts from his enemies. To hammer the argument home she mentions that the people of the Gamma Forests define "Doctor" as "Mighty Warrior".

Later when the prayer leaf is translated from the native tongue of the people of the Gamma Forests to english it reveals that the name Melody Pond becomes River Song, revealing River is their daughter. It also implies a closer history between River and the location. (DW: A Good Man Goes to War)