There used to be a lot of wide, dark spruce forests in the Häme region. Nowadays, one can have a sense of their appearance in conservation areas - for instance in Harju, Loppi, acquired by the Finnish Natural Heritage Foundation in 2003. The following year, the foundation bought an extension to the area with the funds donated by Miss Soile Kulmala to celebrate her Master's degree.

The Harjunmäki 8,6 hectares conservation area consists of Harju forest and a small wetland in Hirssuo. Harju forest of 8,3 hectares is located on a narrow moraine ridge and on the side of it. The wilderness with sturdy spruces casting their shadows over moss and ferns forms the heart of the forest. On the ridge, there are also deciduous trees sighing in the wind, and the flora includes grove species, such as hepaticas and spring vetchlings, typical for ridge areas.

In the wild heart of the forest, there is a ditch that was dug in the 1960s with the first excavator ever seen the village, or so they say. In the autumn of 2007, a restoration project took place with the ditch being dammed to restore the normal water systems.