The reserve covers around 25 to 26 hectares and was formally established in 2010. It comprises two forested rises separated by a narrow cleft known locally as Klämma. The dominant tree is beech, said to have been planted here after the merchant and agricultural reformer Jonas Alströmer acquired land on the hill in 1725. Over the following centuries this planted woodland matured into something closer to natural forest, now containing old, thick trunks and standing or fallen dead wood.
That dead wood supports a notable range of fungi, insects and larvae, including several beech-associated fungal species. Birdlife is also rich, with red-listed species such as the lesser spotted woodpecker and the nutcracker recorded in the area.
The hill has been a popular local walking area since the late nineteenth century, and in 1921 the town of Alingsås bought the land to preserve it as a public amenity. A network of paths, along with walking and cycling routes, crosses the reserve today. On the eastern hill stands a viewing pavilion overlooking much of Alingsås, and beside it a Second World War-era anti-aircraft watchtower, which sources describe as sometimes open to visitors on a seasonal basis, though current access cannot be confirmed here.
Nearby lie other elements of the wider Nolhaga area, including parkland around Nolhaga manor, the shore of Lake Mjörn, and Nolhaga djurpark with its children's farm. A short distance away is the separate Nolhagaviken nature reserve, a wetland at the northern shore of Mjörn and the mouth of the Säveån river, valued for its birdlife and shoreline meadows.