Nova Gorica is a town in western Slovenia, on the border with Italy. Nova Gorica is a new town, built after 1948 when the Paris Peace Treaty established a new border between Yugoslavia and Italy, leaving nearby Gorizia outside the borders of Yugoslavia, thus decapitating the Soča and Vipava Valleys and the north-western Kras Plateau from their traditional regional centre. Nova Gorica is the principal urban centre of the traditional region of Goriška in the Slovenian Littoral. Since May 2011, Nova Gorica is joined together with Gorizia and Šempeter-Vrtojba in a common trans-border metropolitan zone, administered by a joint administration board.