Between the towns of Kamajai and Salos, on the left side of the road, there is not only the much-visited lake Petriošiškis, but also a swamp of especial beauty. Petriošiškis swamp is an important territory for the protection of natural habitats. It is an exemplary ecosystem classified by the European Commission as a NATURA 2000 site. Petriošiškis Reserve was established in 1974, initially operated as Petrošiškis Botanical Reserve-Cranberry Reserve. The reserve includes and protects a swamp (66 ha) and Lake Petrošiškis (60 ha). In the middle part of the swamp there is a high bog, around it – a low bog.