The isthmus is mostly covered by coniferous forests formed by Scots pine ("Pinus sylvestris") and Norway spruce ("Picea abies"), with numerous lakes (e.g. Lake Sukhodolskoye and Lake Glubokoye) as well as small grass, fen and "Sphagnum" raised bogs. Forests cover approximately 11.700 km of the isthmus, more than three-fourths of its total square. Swampy areas occupy on average 5.5 percent of the territory. In the large contiguous area along the shore of Lake Ladoga in Vsevolozhsky District, in the southeastern part of the isthmus, bogs occur much more frequently than in other parts. The same was once true of the lowland along the Neva River, which has been drained. The soil is predominantly podsol, which contains massive boulders, especially in the north and northwest, where large granite rocky outcrops occur.