Ilocos Sur is located along the western coast of Northern Luzon. It is bordered by Ilocos Norte to the north, Abra to the northeast, Mountain Province to the east, Benguet to the southeast, La Union to the south, and the China Sea to the west. Its area of 2,579.58 square kilometers occupies about 20.11% of the total land area of Region 1.
>The topography of Ilocos Sur is undulating to rolling with elevations ranging from 10 to 1,700 metres (33 to 5,600 ft) above sea level.
http://upload.wikimedia.org/wikipedia/commons/d/d5/Ph_locator_map_ilocos_sur.png