Kostivere karst region
is the best-known Karst region in Estonia and the biggest in Harjumaa (its total area is 125 hectares).A large region with the total area of 16 hectares is under state protection. That part of the Karst region is also the most interesting one.
In the Karst region, the Jõelähtme River goes underground near the Kostivere settlement and comes up again near an old bridge in Jõelähtme. Near the river's underground course interesting limestone Karst formations such as open cracks, Karst ditches, funnels, and valleys up to 5 meters deep, can be found.Here are also small caves, the largest of them is Karjakelder that is 6 meters long, 4 meters wide and 2.5 meters high. The bottom of the grotto is always covered with water. Here is also one Karst bridge and peculiar residual rocks known as "stone mushrooms" in the Karst region.
In the Karst field there are 2 - 3 flood periods per year - early in the spring, in the autumn, and sometimes also during a rainy summer. Ditches have been dug above the secret river to facilitate the drainage of the floodwater. In the dry periods the water runs along the flow courses of the secret river that form a complicated underground network. On the basis of electrometrical investigations we can assume that the biggest caves are located in the area between the Tallinn-Narva road and the Jõeste Farm. Most of the Karsts run from north-west to south-east.
In Kostivere Karst region alpine meadow grass (Poa alpina L.) has been found. This graminaceous plant of arcto-alpine origin is very rare in Estonia, as here is the southernmost border of its area. It is also listed in the Red Book of Estonia.
