Along with four national parks, two nature reserves are included in the Laponia World Heritage Area, and Sjaunja is the biggest of those. At 150km long, it sits to the northwest of the E45 and along with Stubba Nature Reserve, its eastern part forms the biggest marsh area in Sweden. Sjaunja's western areas are mountainous. While the Kungsleden runs through the western part of the reserve, Sjaunja is largely difficult to access, with few trails or cabins.

