Joseph Zwaenepoel Forest reserve

Joseph Zwaenepoel Forest Reserve is a strictly protected section of the Sonian Forest (Zoniënwoud/Forêt de Soignes), located on the edge of Hoeilaart, just outside Brussels. It spans more than 187 hectares of old-growth woodland, dominated by beeches over 200 years old. It is one of five parcels of the Sonian Forest that were added to the UNESCO World Heritage List in 2017 as part of the transboundary site "Ancient and Primeval Beech Forests of the Carpathians and Other Regions of Europe."

Why is this forest special?

The reserve was established in 1983 and is classified as an "integral" reserve, meaning the woodland is left almost entirely without human intervention. Fallen trunks, decaying deadwood and natural gaps in the canopy create habitat for fungi, saproxylic insects and birds tied to old-growth conditions — species that are far less common in managed forests. The tall, straight beech trunks, often reaching several dozen metres, give the forest interior a distinctive, column-like appearance that has led people to compare it to a natural cathedral.

What can you do here?

The reserve borders the Groenendaal arboretum and a network of walking trails running through the Sonian Forest, making it a natural starting point for longer walks in the area. Because of its protected status, movement within the core of the reserve is restricted to marked paths — this is a conservation area, not an ordinary city park, so visitors should stay on the trails and avoid wandering off among the deadwood. In autumn, when the beech leaves turn gold and copper and morning mist settles among the trunks, the area draws photographers and walkers looking for quiet so close to the capital.

How to get there?

Hoeilaart lies only a dozen or so kilometres southeast of central Brussels, making the reserve a convenient half-day destination without the need to plan a longer trip. The area is well connected to the Brussels metropolitan region, and the Sonian Forest as a whole is often described as the "green lungs" of the region, visited by both city residents and tourists seeking a contrast to the urban centre.

Frequently asked questions

Can I bring a dog into the reserve? Rules around pets tend to be stricter in integral reserves — it is worth checking the signage on site before visiting, since protecting rare species may require dogs to be kept on a leash or restrict access to designated routes.

Is there an entrance fee? The reserve, like most of the Sonian Forest, is publicly accessible and does not require a ticket — it is public land managed for nature conservation rather than a commercial attraction.

What sets this part of the forest apart from the rest of the Sonian Forest? Its status as an integral reserve means there is no logging or active forestry management, unlike the surrounding, actively managed parts of the Sonian Forest — this has allowed the trees to reach a naturally advanced age and structure.

Can a visit be combined with other attractions in Hoeilaart? Yes, the Groenendaal arboretum and Groenendaal Castle are both nearby, allowing the trip to be extended with additional stops without travelling elsewhere.