The 21,5-hectare Topenginleija Conservation Area in Kaurissalo, Kustavi, developed in 2007 as a result of two purchases. In the early autumn, the Finnish Natural Heritage Foundation bought an 11-hectare swamp with its surrounding forests, and late in the year, the foundation acquired an additional area of 10,5 hectares consisting mainly of rocky forest.
The diverse Topenginleija Area with all its swamps and different kinds of forests has both ecological value and a valuable landscape. Having a lot of water in the surroundings, Topenginleija is different from the foundation's other conservation areas, which are firmly standing in the mainland.
The northern part of the Topenginleija Conservation Area is labelled by an open, undrained swamp. It used to be a strait, which the rising of the earth turned into a certain kind of lake and then into an open bog. This process has left a little boghole there. In the middle of the swamp and in the surroundings, there are common alders growing in the wilderness with the decaying wood and the water hollows laying a foundation for all kinds of species to live a life there.
On the edges of the open bog, there are small knolls where the forest has had a chance to develop in peace. Some of the most considerable details in this diverse forest are the giant aspens, the pine trees with their bark resembling a carpet of shields as well as the large, old birches.
In the southern part of the conservation area, the terrain rises and turns into rocks. On the slopes, one can see some diverse heath forests, which turn into old pine forests at the top. The oldest pine trees are about 165 years old.