Lonjsko polje has been officially called Nature Park since March 6, 1990. The size of the Park is 50650 ha, (506 km²). The North border of the Park is highway Zagreb-Slavonski Brod, and the south border is the river Sava.
Lonjsko polje is a swamp area and it is listed as the most endangered habitat in the world. It is the biggest protected swamp area, not only in Croatia but also in the entire Dunav river system. It is enlisted in so called Ramsarsic list of swamps that are of international importance, especially as a habitat of swamp birds. According to European Union bird directive, that area belongs to the Important Bird Area – IBA.
Along the entire Sava stream and its left streams have a mild drop of the river level which results in the slow water runoff, a lot of flooding and long holding of the water on the area. If there is a sudden high water level in all the rivers, the amount of the water collides and causes floods. The area of middle Posavina can take up to two billion m³ of water.
On the area of Lonjsko polje there are two ornithological reservations. Krapje Đol has been proclaimed a special zoological (ornithological) reservation in 1996, and it spreads over 25 ha. Rakita, with the area of 430 ha, has been proclaimed a special ornithological reservation in 1969.
Grassland complex of Lonjsko and Mokro polje have, along with domestic Simmental cattle, the highest concentration of indigenous species in Croatia. The indigenous species such as: Croatian Posavic horse, Croatian Cold blood horse, Turofield Pig and Slavonian-Sryemic Podolic Cow are the basis of local economy.
Ethno social resources
In Lonjsko Polje ethno social resources are important. They include national costumes, crafts and gastronomic skills, and also different kinds of nonmaterial cultural heritage which includes language (specific dialect), folklore, ceremonies, and traditional arts and crafts.
Biological importance of Nature Park Lonjsko Polje is mostly visible in its ornitho-fauna, the bird species that have a permanent of temporary habitat here. It has been confirmed that there are 250 different species of birds, out which 134 of them are the nesting birds. There are two species of birds that are on the list of world’s endangered species: white-tailed eagle crake pointer, and about 30 species that are endangered in Europe: black stork, lesser spotted eagle, and spoonbill.. Lonjsko polje is one of the habitats with the most concentration of white storks. In 1988 there have been 580 couples of storks, out of which 51 was in the village Čigoć, so in 1994 Čigoć has been proclaimed a European stork village. The white stork is a bird that nests on the rooftops of wooden Posavic houses.
Today, Nature Park Lonjsko polje is the only area that authentically represents the historic age from 15th to 19th century. It is the area of an extraordinary adjustment of population to floods, which is shown in their traditional wooden architecture, spatial organization and the use of land and the unique breeding of authentic cattle used to the conditions of life there. The flood system is based on lifting the house from the ground on poles and building a one storey houses. Upper part of the house has always been safe from the floods. The picturesque of the houses is emphasized by covered stairs, porches and roofs.