Border Keeps are the two keeps that form the main bases for the three Alliances. These areas cannot be taken over or even attacked by the opposing Alliances. The only way in or out requires the use of a gate which can only be used by the Keep's controlling Alliance. Since it is not possible to enter the opposing Alliances' Border Keeps, you will only have access to the two of them which belong to your chosen Alliance. Each pair is linked on the Transitus Network, and travel between them is thus always possible as this is the one link which can never be broken via siege. The Border Keeps contain all of the vendors in Cyrodiil, including Siege Merchants and Mercenary Merchants, which can be found nowhere else. They also are home to the only Wayshrines in Cyrodiil, which are your means of returning to the PvE areas.
List of Border Keeps
Aldmeri Dominion
Eastern Elsweyr Gate — A border keep in southern Cyrodiil, far south of the Imperial City. (map)- Western Elsweyr Gate — A border keep in southern Cyrodiil, far south of the Imperial City. (map)
Daggerfall Covenant
Northern High Rock Gate — A border keep in northwestern Cyrodiil, far northwest of the Imperial City. (map)- Southern High Rock Gate — A border keep in northwestern Cyrodiil, far northwest of the Imperial City. (map)
Ebonheart Pact
Northern Morrowind Gate — A border keep in northeastern Cyrodiil, far northeast of the Imperial City. (map)- Southern Morrowind Gate — A border keep in northeastern Cyrodiil, far northeast of the Imperial City. (map)