The Kree Foothills are the birth place of Aidan. It is a location in the Shiverpeak Mountains. (Aidan's mother died giving birth to him while his family was on a wagon trail from Kryta to Ascalon.) The exact location of the Kree Foothills is unknown.
Note: "Kree Foothills" has in the past been the name of two in-game locations, which have since been renamed, one to Borlis Pass (during beta) and one to Yak's Bend. In addition, the most recent official Guild Wars website now lists Aidan's birthplace as "Borlis Pass" rather than "Kree Foothills", which indicates that Arena.net are continuing with phasing out all the old location names.