The site of Vrela Cetine, the spring of the Cetina River, covers an area of 29.81 ha and was protected in 1971.This site contains a series of karst springs. The three main springs, Veliko vrilo, Vukovića vrilo and Batića vrilo, lie along the edge of the Paško polje or Pag Field, in the foothills of the Dinara mountain range. All the springs were formed at the site of contact of permeable marl in the field and water impermeable limestone of the surrounding plateaus. The springs draw attention with their magnificent clarity and blue-green colour. Veliko vrilo, also called the Glavaš spring, is a submerged speleological structure, which divers have investigated to a depth of 150 m. Near the springs is the oldest Early Croatian church in Croatia, the Church of the Holy Salvation (Sv. Spas). The church belongs to the pre-Romanesque style with a bell tower, and was erected in the 9th century. Next to the church is a cemetery with tombs (traditional stone headstones) dating back to the 14th and 15th centuries.