The Warsaw-Berlin Proglacial Valley stretches latitudinally from Warsaw to Berlin. Its latitudinal stretch is caused by the former ice sheet blocking the outflow of rivers to the north and creating an ancient river flowing westwards. Currently, the area includes the valley of the Bzura and Ner rivers and their tributaries. At the level of Łęczyca there is a watershed between the Odra and Vistula catchment areas.
At the level of Łęczyca the watershed between the Odra and Vistula catchment areas runs, from where some waters flow westwards and some eastwards. The valley bottom is about 2 km wide in this area and is filled with peat. The extensive marshes have been drained since the 19th century by an extensive drainage network and the rivers have been regulated. Extensive meadows and pastures were created.
In the area around Łęczyca, peat was extracted intensively before World War II, leaving so-called peat ponds. Despite such drastic human interference, the natural wealth of the valley, although diminished, is still impressive. The nature has adapted to the above mentioned changes - the peat bogs have been filled with water and mud vegetation, mainly reed and sedge rushes, and they have also become a sanctuary for fauna. Extensive cultivation of meadows and pastures favours the occurrence of rare plant communities and protected bird species. The valley is also one of the longest animal
The valley is also one of Europe's longest migration corridors for animals, including birds, which during migration form groups of several thousand individuals, thus creating a spectacular show. Farmers with arable fields on the slopes of the Pradolina have sometimes complained, that during one night a large flock of geese consumed wintering wheat in a field covering several hectares. In contrast, the birds, for which the valley is a breeding ground, lead
in most cases secretive, and observing them requires persistence. The richness of the valley's flora and fauna has a positive influence on neighbouring areas, mainly agricultural, favouring the settlement of many animal species for which the valley is a feeding ground. The lack of need to use protective measures on uncultivated land, meadows and pastures favours the preservation of its ecological purity, thanks to which both bees and other insects find here feeding grounds and places to live, and hay obtained from this area by farmers constitutes excellent fodder. The largest fishponds in central Poland, Okręt and Rydwan (250 ha), a complex of ponds in Walewice (210 ha), Psary (180 ha) and Borowo (120 ha), and other reservoirs have been created here. Some of them were dug as early as in the Middle Ages. A curiosity are the saltmarsh plants found near Łęczyca, which locally find conditions for vegetation thanks to their specific geological structure - a salt pan. Currently, out of 155 bird species nesting in the Pradolina, the following should be considered particularly valuable: aquatic warbler, greylag, platypus, sandpiper, eagle owl, bittern, marsh harrier, Montagu's harrier, spotted eagle owl, corncrake, stonechat, redshank, curlew, curlew, little tern, black tern, bluethroat, redshank, white-tailed eagle, crane, green sandpiper, osprey, lapwing. Migrating birds, which rest and feed here, usually exceed 20,000 individuals, even reaching 67,500. Because of its natural values, the valley has been recognised as valuable and placed under protection in accordance with EU legislation: the Birds Directive and the Habitats Directive (protection of habitats), as well as national forms of protection. There are also other animals living here: roe deer, elk, fallow deer, deer, wild boars, raccoons, foxes, otters, muskrats, beavers, bats. There are also valuable species of insects, fish, amphibians, reptiles and crustaceans.