River Song's World

River Song's World was an alternate timeline created by River Song when she altered a fixed point in time by preventing the Doctor's death. In this timeline all of Earth's history occured simultaneously: the War of the Roses entered its second year, dinosaurs walked the Earth and Winston Churchill was the Emperor of the Holy Roman Empire.

History
On 22 April 2011 the Doctor met River Song, who was wearing an astronaut suit, at Lake Silencio on Earth. He told her that he knew she was the one who was going to kill him and that he forgave her. River, however, drained the suit of its power supply making it impossible for her to kill the Doctor. This created the new timeline. (DW: The Wedding of River Song)

Although he had no knowledge of the original timeline, Emperor Churchill was able to sense that something was wrong because the time and date never changed. Churchill had the Doctor, known in this world as a soothsayer, brought to him and demanded he explain why the time never changed. After revealing how this timeline was created, the Doctor and Churchill were attacked by the Silents only to be rescued by a group of soldiers led by the alternate Amy Pond. The alternate Amy Pond remembered certain things about her travels with the Doctor in the original timeline, but initially couldn't remember that Rory Williams (one of her soldiers) was her husband or that River Song was their daughter.

This alternate timeline was ended when the Doctor convinced River Song to "kill" him, thus restoring the original timeline.