Kőérberek Sodic Meadow aka Bitter Water Spring is the only sodic field of Budapest and has a protected status for its special fauna and flora. It is located close to the Airfield of Budaörs and Egér Street. Although it seems neglected it is a unique value due to is special soil and wildlife.

Its formation was different from sodic areas of the Plain as it was the evaporation of sulfate-rich waters from the nearby Őrsöd hills that provided the necessary circumstances for the process.

The former owner of the 42 hectare area dug a well in 1862, however, water was too bitter to drink. Baize trader András Saxlehner ordered tests and discovered the valuable mineral content of the water. After building the necessary infrastructure he began to sell curative water called “Hunyadi János Water” rich in sodium-sulfate and magnesium-sulfate. By today it has become a well-known curative water with laxative effect. Sulfate content probably originates from the disintegration of pyrite grains just a few meters deep below surface.

Water from the neighboring area is sold under the name of “Ferencz József” rich in Glauber’s salt. In fact, these mineral waters are from ground water, thus sensitive to surface pollution. As a way of prevention a conversation area was set up to protect water sources.

Human activities also served maintenance of the meadow. Grazing and reaping prevented the growth of shrubs and trees. Sodic flora appeared due to minerals accumulated in ground water. Drainage trenches reduce ground water level decreasing salt concentration and posing the danger of dry-up. Recently shrubs and trees started to grow but by taking the necessary land management steps the process is reversible.

The sodic meadow has had a natural reserve status since 1982 and is not open to visitors for the protection of wells and flora.