Swallow Woods was located in England. An alien ship crashed there during the Bronze Age. It caused time and space distortions in the woods due to being damaged. The ship normally learned from travelling and would eventually achieve self-awareness in a process called the Shift. To gain knowledge while stranded on Earth, every fifty years it would take a person passing through the woods and learn from their experiences. By 1917, when it abducted Rory, the ship had taken 173 people.
The Eleventh Doctor, Amy and Rory helped the ship complete the Shift and depart Earth. This caused the distortions to be repaired, and all but 3 of the disappearances to have occurred in an alternate timeline. (PROSE: The Way Through the Woods)