Pecs is the fifth largest city of Hungary, located on the slopes of the Mecsek mountains in the south-west of the country, close to its border with Croatia. It is the administrative and economic centre of Baranya County. Pecs is also the seat of the Roman Catholic Diocese of Pecs. The city Sopianae was founded by Romans at the beginning of the 2nd century, in an area peopled by Celts and Pannoni tribes. By the 4th century, it became the capital of Valeria province and a significant early Christian center. The early Christian necropolis is from this era which became an UNESCO World Heritage Site in December 2000.