The Bílichovské údolí (Bílichov valley) NNM lies around 2km south-west of the village of Bílichov in the north-west of the Středočeský kraj – Central Bohemian Region. The monument lies on a steep north-east facing slope in the valley of the Zlonický potok Stream at elevations of 380-420 metres above sea level.
The territory was first protected in 1933 and was re-declared as a national nature monument in 2007 on an area of 8.48ha. the main subject of the protection is the critically endangered black false hellebore (Veratrum nigrum) which grows in part of the beechwood with helleborines.
Bílichovské údolí NNM lies in the natural forest region of the Středočeská pahorkatina Hilly land, and on the north-western edge of the Džbán Cretaceous Massif, which is built of strata of Cenomanian clays and claystones, Cenomanian sandstones, soft marls and hard Lower Turonian opokas (marlites). The impermeable layers below the hard opokas form a distinct aquifer, which is typical for the Džbán region. Several slope springs can be found in the monument, especially on the lower slopes along the stream. These spring enabled the formation of small slope marshes and fens at various stages of development and small landslips.
The black helleborines grow on the slopes in the more open forest stands around the springs, and often in places where the soil is humus-enriched and similar to fen peat. The optimum conditions are found in forest stands with a stand density of around 80% and in glades in the closed forest stands. The helleborines produce dark-purple flowers in mid-summer and these black helleborine flowers are known as “black royal candelabra”. Other interesting species which occur here include the highly-endangered red and white helleborine (Cephalanthera longifolium) and the saprophyte pinesap Hypopithys monotropa.
The current enclaves or sporadic occurrence of the black helleborines in and around the specially protected area is probably caused by the compartment felling forestry methods and the introduction of conifers in place of forest stands with a higher proportion of deciduous trees. The black helleborines previously grew abundantly and throughout the natural forest stands at varying densities. The black helleborines have retreated from the new and closed forests. Fragments of the helleborine population have only survived in natural glades around small landslips. A contiguous growth of the Japanese lantern plant (Physalis alkekengi) grows casually at the foot of the slope.
The territory of the national nature monument is accessible by the general public.