Geological natural monument "Geological outcrops of Devonian and Ordovician rocks in the river Saba" was organized in 1976. It is located 3 km from the village Osmino, near the village of Psoed. Area geological monument is 650 hectares.

The territory of the natural monument is organized in order to protect the output of geological rocks of the Ordovician and Devonian to the surface, as well as the preservation of the remains in the Devonian sediments armored fish.

Investment attractiveness of the reserve is obvious. This natural monument can be good for the organization of excursions in protected areas Luga and Gatchina districts.

Saba River Valley on the site, which begins at two kilometers above the village Psoed and ends at 3, 5 km downstream from the village Osmino, has a trough-shaped cross-section profile. The width of the valley - 250-300 meters. The width of the river is 20-25 m and has a depth of 0, 1, 3, 5 m. The river - quiet, typical of lowland rivers Russian North-West. Valley has submeridional orientation from north to south. Riverbed meanders within the rectilinear valley. Where to wash the root shore out to the surface of red sandstones of the Devonian age, they found remnants of mineralized fossils and prints armored fish.

The total occurrence of layers - close to horizontal, in some horizons, there is a clear cross-bedding. Outcrops raised above the water's edge to 1-6 m, sometimes 12-15 m. The length of the outcrops varies from a few meters to hundreds of meters (in some areas). The vegetation is severely impaired because of economic activity, which was the result of development of the given area and the close proximity of human settlements. Anthropogenic pressure on vegetation expressed in deforestation, mainly near settlements, clogging of the territory, fires, destruction of the slopes, plowing areas along the river, trampling. On the banks of Saba are marked areas of small-leaved and broad-leaved forests, they are the most advanced on the cliffs, in particular, in the vicinity of Osmino.

Among the representatives of deciduous trees are most common Ulmus glabra, which reaches a height of at least 15 m, also reported ash, elm, oak, linden, maple. The grass-bush cover the predominant species are those that are associated with deciduous tree species. Among them - goutweed, bluegrass groves, Zelenchuk yellow Dubravnaya chickweed, chickweed lantsetolistnogo, common Dryopteris male, lily of the valley, bell, etc. persicifolia. Pine forests are recovering after fires lugovikovymi pine forests. Also recorded fragments Landysheva pine. Small-leaved forests are seroolshanikami.

Most of the territory occupied by the monument of natural grasslands. Short grass meadows that grow on the site of fires consist of Jasione Montana, cat's paw, clover field, sticky tar, sedges vereschatnikovoy, zhabnika field. On the left bank of the Sava near the village Psoed locally. Affected once the fires are marked with meadows ling. In such dry meadows uncommon: lichen reindeer moss and bushy lichens of the genus Cladonia. In moderately wet areas - meadows Bell overcrowding, mullein black, oregano and others. In the wetter areas near the water's edge are located high-grass meadows, where there are Veronica longifolia, Angelica archangelica, yellow meadow-rue, Siwiec Field and others. In previously mowed meadows, has now turned into deposits, along with forage grasses grow sorrel, bent grass thin, St. John's wort.

In the vicinity of Osmino celebrated a rare species Repeshko pharmacy. In addition, the raw nezadernennyh banks of the river there Coin-loosestrife, Ranunculus repens, mint field zherushnik amphibians. Coastal water and aquatic vegetation is represented horsetail river, arrowhead ordinary, Potbelly zheltoychastuhoy plantaginaceae, reed, bulrush, vehom, Manica large iris yellow sparganium direct, meadowsweet and meadowsweet naked sedge sharp, Lythrum salicaria, there are also small courtines buttercup longifolia, a rare species of broadleaf porucheynika.

On the territory of specially protected natural monument: exposure of the Devonian period, the fossils of plants, animals, rare plants: moonwort Multiple partition, Jasione Montana, kolyuchnik Finnish. It is prohibited to construction, mining and land reclamation works, lining of any communications, plowing, littering territory.