The biggest town of Western Serbia is Valjevo, interesting for its old centre of cobbled streets with numerous craftsmen's workhops and old-fashioned houses built in the traditional Balcanic style that have preserved the spirit of the old days. The valley of Dobri Potok, with its old wooden church, mysterious tombstones and an etnological museum is also an interesting spot not to be missed. Mountains Maljen and Povlen are covered with an extensive network of hiking paths and lodges, not to forget the medieval monasteries hidden in the lush forest. The Gradac rives is considered to be one of the cleanest rivers in Serbia.