The Kaproun NNM covers an area of 2.92 hectares in the parish of Kaproun, which lies between the towns of Kunžak and Nová Bystřice in the east of the Jihočeský kraj (South Bohemian Region). The locality was first protected as a natural formation in 1987 and transferred to the category of national nature monument in 1992. The monument lies in a terrain depression around the upper (spring) reaches of the Dračice stream and is covered with waterlogged spruce stands with mosses of the Mastygobryo-Piceetum association.
The main subject of the protection is a remnant population of the critically endangered narrow-leaved marsh orchid (Dyctylorhiza traunsteineri) growing on a meadow peatbog. The vegetation consists of sedge communities of peaty meadows of the Caricion fuscae alliance passing into moor-grass communities (Violion caninae alliance). Notable plant species which grow here include marsh cinquefoil (Potentilla palustris), hare’s-tail cotton-grass (Eriophorum vaginatum), bogbean (Menyanthes trifoliata), star sedge (Carex echinata), the small cranberry Oxycoccus palustris, the ragwort Tephroseris crispa, viper’s grass (Scorzonera humilis), the brown moor clover (Trifolium spadiceum), mountain arnica (Arnica montana) and Willemetia stipitata of the aster family. An abundant population of the narrow-leaved marsh orchid (Dactylorhiza traunsteineri) was discovered here in 1976, but this orchid nearly became extinct when the surrounding lands were drained. The orchids have flowered here again on a regular basis since 1995 with 9 flowering examples at the locality in 2008. A narrow littoral fringe of tall bottle sedges (Carex rostrata) grows around the pond which is also part of the monument. The water horsetail (Equisetum fluviatile) also grows here and the white water lily Nymphaea candida grew here abundantly until 1988.
Several mollusc species live in the pond, including the specially protected duck mussel (Anodonta cygnea). A total of 23 dragonfly species develop in the drainage ditch where their larvae are protected from the predatory pressure of fish. The protected ground beetle Carabus arcensis, the tyrphophilous ground beetle Plerostichus diligens, the uncommon humicolous rove beetles Stenus latifrons and Astenus brevelytratus and the rare weevil Apion sorbi all live in the protected area. Notable occurrences of Diptera insects at the site include the rare and little-known frit fly Elachiptera diastema of the Chloropidae and the fungus gnat Brevicornus sericoma. Common toads (Bufo bufo) and moor frogs (Rana arvalis) breed in the pond, whereas the pool frog (Rana lessonae) lives in large numbers in the drainage channel.