The Sisters of the Infinite Schism was, according to the Eleventh Doctor, "the greatest hospital in the universe."
Amy, Rory and the Doctor took River Song there to recuperate after she had sacrificed her powers of regeneration for the Doctor. Because the version of River in the hospital was much younger than the one the trio had known, they left her there. River would start her education in archaeology, setting her on a path to rejoining the Doctor for the adventures he had already experienced. (DW: Let's Kill Hitler)