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Published on March 14, 2026

Sonian Forest: A Guide to Brussels' Green Lung and Outdoor Activities

Just a stone's throw from the bustling heart of Brussels lies a vast, ancient woodland known as the Sonian Forest. Often referred to as "Brussels' Green Lung," this magnificent forest offers an unparalleled escape into nature, inviting locals and tourists alike to explore its serene beauty and diverse outdoor activities.

What is the Sonian Forest?

The Sonian Forest (Forêt de Soignesin French,Zoniënwoudin Dutch) is a sprawling deciduous forest covering over 4,400 hectares (approximately 11,000 acres) across the three Belgian regions: Brussels-Capital, Flanders, and Wallonia. Historically, it was part of a much larger primeval forest, the Carbonaria Forest, which once stretched across central Europe. Today, it stands as a cherished natural heritage, characterized by its majestic ancient beech trees, some standing for over 200 years.

This remarkable natural area is not just a recreational spot; it's a vital ecosystem. It plays a crucial role in purifying the air around Brussels, supporting a rich biodiversity, and offering a tranquil refuge from urban life. Its sheer size and ecological importance make it one of the most significant green spaces in Belgium.

A UNESCO World Heritage Site

In 2017, parts of the Sonian Forest were inscribed as a UNESCO World Heritage Site as part of the "Ancient and Primeval Beech Forests of the Carpathians and Other Regions of Europe." This prestigious recognition highlights its exceptional universal value as an outstanding example of undisturbed temperate forest ecosystems and a testament to the post-glacial expansion of beech forests in the Northern Hemisphere.

Did you know?The UNESCO designation specifically covers the forest's "relict" parts, meaning areas where the ancient beech forests have been preserved with minimal human intervention, showcasing the natural evolution of these magnificent woodlands.

This status underscores the forest's importance not only for Belgium but for the entire world, emphasizing the need for its continued protection and sustainable management.

Getting to the Sonian Forest

One of the Sonian Forest's greatest advantages is its accessibility from Brussels. Whether you're relying on public transport or driving, reaching this natural haven is straightforward.

  • By Public Transport:Numerous tram, bus, and metro lines connect Brussels to various entry points of the forest. For example, metro line 5 to Herrmann-Debroux, tram 8 to Wiener, or bus 41 to Hoeilaart provide direct access to different sections. Check local transport apps for the most convenient route to your desired starting point.
  • By Car:The forest is easily reachable by car, with several parking areas located around its perimeter, especially near popular activity zones and visitor centers. Be mindful of parking regulations and respect designated areas.
  • By Bike:For those already in Brussels, cycling to the forest is a great way to start your outdoor adventure, with dedicated cycle paths leading from the city into the forest.

Activities in the Sonian Forest

The Sonian Forest is a playground for nature lovers and outdoor enthusiasts, offering a wide array of activities suitable for all ages and fitness levels.

Hiking and Walking

With an extensive network of marked trails, the forest is a hiker's paradise. You can choose from short, leisurely strolls on paved paths to more challenging treks through dense woodland. Many trails are clearly signposted, guiding you through serene beech avenues, along babbling brooks, and past historical landmarks.

  • Family Walks:Shorter, well-maintained paths are perfect for families with young children or those seeking a gentle walk.
  • Long-Distance Hikes:For the more adventurous, longer routes connect different parts of the forest and even link up with regional walking networks.
  • Themed Trails:Look out for specific trails that highlight historical sites, unique flora, or offer accessible options.

Cycling and Mountain Biking

Cycling is another popular way to explore the forest. There are designated cycling paths and mountain bike trails that wind through the diverse landscapes. Cyclists can enjoy both paved routes and more rugged off-road tracks designed for mountain biking, ensuring a thrilling experience while respecting the forest's ecology.

Always stick to marked paths to protect the sensitive ecosystems and ensure your safety. Bike rentals are available in some areas adjacent to the forest for those without their own equipment.

Horse Riding

Equestrian enthusiasts will find dedicated horse riding trails that allow for a unique perspective of the forest. These trails are separate from walking and cycling paths, ensuring a safe and enjoyable experience for riders and other forest users.

Nature Observation and Photography

The Sonian Forest is a haven for wildlife. Keep an eye out for deer, foxes, wild boars, and a variety of bird species, including buzzards and black woodpeckers. Its diverse flora, especially the impressive beech trees, makes it a fantastic spot for nature photography throughout the seasons. Spring brings vibrant greens and blooming wildflowers, while autumn transforms the forest into a spectacular palette of reds, oranges, and golds.

Picnics and Relaxation

For those seeking a more relaxed experience, numerous designated picnic areas are scattered throughout the forest. These spots offer a perfect opportunity to enjoy a meal amidst nature, listen to the sounds of birds, and simply unwind. Find a quiet bench or a grassy clearing and soak in the tranquil atmosphere.

Family-Friendly Fun

Beyond walking, the forest offers several attractions for families. Some areas feature playgrounds, while nature centers provide educational exhibits about the forest's ecology and history, often organizing guided walks and workshops for children.

Historical Sites within the Forest

The Sonian Forest also holds historical significance. Within its bounds, you can discover remnants of ancient abbeys, chapels, and old fortifications, offering a glimpse into its past. These historical elements add another layer of discovery to your visit, blending nature with heritage.

When to Visit the Sonian Forest

The Sonian Forest is beautiful year-round, with each season offering a unique charm:

  • Spring (March-May):Fresh green leaves, blooming wildflowers, and the return of migratory birds. Perfect for vibrant photography and crisp walks.
  • Summer (June-August):The dense canopy provides welcome shade on hot days, making it ideal for long hikes and picnics.
  • Autumn (September-November):Arguably the most spectacular season, with the beech leaves turning brilliant shades of yellow, orange, and red. A photographer's dream.
  • Winter (December-February):A serene and quiet beauty, especially after a snowfall. The stark silhouettes of the trees create a dramatic landscape, ideal for peaceful contemplation.

Respecting the Environment: Tips for Visitors

To ensure the Sonian Forest remains a pristine natural treasure for generations to come, visitors are encouraged to follow a few simple guidelines:

  • Stay on Marked Paths:This helps protect fragile ecosystems and prevents disturbance to wildlife.
  • Leave No Trace:Take all your rubbish with you.
  • Respect Wildlife:Observe animals from a distance and avoid feeding them.
  • Dogs on Leash:Dogs are generally welcome but must be kept on a leash in most areas to protect wildlife. Check specific signage for designated off-leash zones.
  • No Open Fires:Fires are strictly prohibited to prevent wildfires, especially during dry periods.

Beyond the Sonian Forest: Exploring Nearby

While the Sonian Forest offers endless exploration, Belgium is rich with other natural and cultural gems. If you appreciate the tranquility of the forest, you might also enjoy a visit to the breathtaking Hallerbos Forest, famous for its magical bluebell carpet in spring. Further afield, the rugged beauty of the Ardennes Hills, the diverse landscapes of Hoge Kempen National Park, or the serene Eifel Natural Park offer different outdoor adventures.

For a contrast to nature, Brussels itself boasts iconic attractions like the magnificent Grand Place, a UNESCO World Heritage site that showcases Belgium's rich architectural heritage. Combining a visit to the bustling city with a rejuvenating escape to the Sonian Forest offers a complete Belgian experience.

The Sonian Forest is more than just a forest; it's a living, breathing part of Belgium's natural heritage, providing an essential green sanctuary for both people and wildlife. Whether you're seeking an invigorating hike, a peaceful picnic, or simply a moment of calm amidst ancient trees, this "Green Lung" of Brussels promises an unforgettable experience.