Soos NNR is located 5 km NE of the centre of the spa town of Františkovy Lázně and 3.5 km SE of Skalná. The reserve covers an area of 221 ha at elevations of 429 – 440 metres above sea level in the parishes of Vonšov (Nový Drahov), Dvorek and Nová Ves and was declared in 1964.
Soos is an example of a unique territory on a pan-European scale and includes a wide variety of biotopes and their transitional phases. On the NNR territory we can find peatbogs and fens with numerous issues of mineral water and emanations of gaseous carbon dioxide (CO2), extensive water surfaces and small streams. The central part of the reserve contains a notable diatomite deposit, saturated with mineral salts. Local plant communities represent a varied mosaic of the vegetation of high-moor bogs, transitional peat-bogs, fens, halomorphic soils and communities which are directly influenced by the CO2 gas emanations. The diversity of animal species, especially of invertebrates, amphibians and birds, is also of exceptional natural value.
A themed nature trail leads visitors to valuable localities within the reserve. The visitors can also attend an exposition of the current nature and the history of the locality. A sanctuary (rescue station) for handicapped animals is also open to the public.
The Soos NNR lies in the central part of the Cheb Basin. The basement is formed of crystalline rocks and a pile of sediments up to 180 metres thick. The upper strata are composed of organogenic sediments (humolites), with some material from the nearby kaolinic sands and clays of the Vildštejn Formation. The morphologically distinctive basin was formed on this geological background and is filled with organogenic sediments of Holocene age up to 5 metres thick. At Soos, these sediments are of a wide variety of types, which is the result of the variable chemical composition of the aquatic environments in which they were formed.
Fens of the humolite type were predominantly formed in the central and southern parts of the NNR, in areas with waters of a sodium-hydrogencarbonate type and also where the waters with low content of dissolved solids mixed with acidulous waters of a sulphate-hydrogencarbonate-chloride-sodium type with high contents of dissolved solids. Sulphur-iron-rich fens have formed in some areas on the diatomites. Fens with pyrite content (mostly black or more rarely in the form of silver crystals several millimetres in diameter) where the sites favourable for the origin of limonite and palliardite as well as minerals formed by water evaporation such as sodium sulphate, sodium carbonate, calcium sulphate and sodium chloride. Ferrous sulphate and ferric sulphate can be also found at places where the diatomites are exposed to air oxidation. Especially in dry periods these minerals form extensive salt efflorescences in areas without vegetation (its growth is inhibited by extremely acidic soil and water environment due to the effects of sulphuric acid).
A number of plant communities have formed at the Soos NNR due to the variety of biotopes found here (and the transitions between them). The most important plant communities are found on the peatbogs, fens and their transitional stages. The many rare and protected plant species which can be found here include the pale bladderwort (Utricularia ochroleuca) and intermediate bladderwort (Utricularia intermedia), one-flowered wintergreen (Moneses uniflora), bog sedge (Carex limosa), reddish pondweed (Potamogeton alpinus), round-leaved sundew (Drosera rotundifolia), the viper’s grass Scorzonera parviflora, white beak-sedge (Rhynchospora alba), the spurrey Spergularia salina, sea milkwort (Glaux maritima) and others. Fungi which are found here include the bolete Suillus flavidus and the cup fungus Otidea concinna.
The varieties of natural habitats which form a mosaic at the Soos NNR are the home of a great many protected animal species. Notable invertebrates which have been found here include the butterflies poplar admiral (Limenitis populi), scarce swallowtail (Iphiclides podalirius) and swallowtail (Papilio machaon), lesser marbled fritillary (Brenthis ino) and cranberry blue (Vacciniina optilete) as well as the fishing spider (Dolomedes fimbriatus) and the great Capricorn beetle (Cerambyx cerdo).
Among the vertebrates, the bird populations are of the great significance and we can find the crane (Grus grus), white-spotted bluethroat (Luscinia svecica cyanecula), common redshank (Tringa totanus), snipe (Gallinago gallinago) and marsh harrier (Circus aeruginosus). Reptiles and amphibians are represented by the common toad (Bufo bufo), the rare natterjack toad (Bufo calamita) and edible frog (Rana esculenta), the more common frog (Rana temporaria), Alpine newt (Triturus alpestris), sand lizard (Lacerta agilis) and viviparous lizard (Zootoca vivipara).