HIKING POINT Sonian Forest

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20.5 km
186 m
04h05
Hard

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Last verified: 10 April 2025
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Description by the author

The Sonian Forest is a vast forest area in the heart of Belgium.

Immerse yourself in an endless beech forest with trees like cathedrals. Walk on wide hiking trails or narrow, winding paths that find their way through small valleys with streams and lakes.

Discover a mysterious stone circle and a dolmen, two very special memorials.

Bring your own picnic into this large forest, because along the way you will find only trees and greenery.


The Sonian Forest

The Sonian Forest is located in the heart of Belgium, just south of the capital Brussels. It is located on the territory of the Flemish, Walloon and Brussels regions. This beautiful forest is no less than 44 km2.

This vast forest area is a remnant of the primeval forest that stretched from the North Sea to the Rhine in Roman times. Julius Caesar named this forest the "coal forest" (Silva Carbonaria) because coal burners were at work. They burned charcoal to extract iron from ferrous sandstone.

Until the end of the Middle Ages, the intact forest was the property of the nobility and several monasteries. But in the 16th century, the Austrian Habsburgs had the trees replaced by planted beech trees. These beech trees still form the "beech cathedral": an open forest with giant beech trees that can be up to 200 years old. Some of these giants are uprooted in stormy weather, you will find quite a few fallen trees along the way.

Today, nature management replaces part of the beech trees with a more varied forest with a higher ecological value.

The walk

The walk plunges you into the beech forest. Do not expect beautiful views in such a forest, but the green security of a vast forest area.

The Sonian Forest has always been covered with trees and agriculture has never been practiced. As a result, you can always recognize the natural relief in the forest. There are wide hiking trails on flat ridges where you can quickly make for miles. And there are narrow, winding paths in shallow valleys with streams and ponds. In the cathedral forest with giant beech trees you can see quite far through the trees. Where these giants have been replaced by more varied forests, you look no further than a few meters away.

The walk passes two remarkable monuments, which form a quiet harmony with the forest that surrounds them.

The memorial to the victims of the attacks of March 22, 2016 commemorates the 32 victims with as many beech trees. They stand in a circle around a ring of stone, Belgian blue stone. The monument to foresters who died during the First World War commemorates 12 victims with the same number of megaliths. These are also in a circle, with a dolmen in the middle. The stones consist of the same conglomerate that was used in Wéris in prehistoric times.

This walk takes place more than 99% on unpaved roads and only crosses a highway twice. The route avoids bridle paths (which are often made of loose sand) and bike paths (which are usually paved).

When

In the Sonian Forest you can take a nice walk at any time of the year.

In spring, there is a lot of light, and the beech trees turn fresh green. During the summer, there is not much sun under the tall trees, but it remains beautiful and cool. In autumn, the trees look beautiful when the leaves fade. Mushrooms grow everywhere, and you can pick chestnuts at two places along the road. On rainy winter days, the trees provide enough shelter to keep it a little dry.

The Sonian Forest is a nature reserve, so you should not pay attention to striking hunters. To spot wildlife, you need to get out early in the morning. Wild boars are very shy, but with a little luck you can see deer.

This forest is the garden of all Brussels residents, so it is very busy, especially during the weekend. Fortunately, the area is very large and it becomes much quieter as you move away from the capital.

Point of departure and arrival

Groenendaal Castle

Address: Duboislaan 1, 1560 Hoeilaart

- By car: there is ample parking.

- By public transport: smooth rail link from Brussels to Groenendaal station. Then another 1.5 km walk to Groenendaal Castle.

Practical information

At Groenendaal Castle there is the trendy tavern 'Sonian' where you can eat and drink something.

www.sonian.be

Not far from the starting point is the forest museum 'Jan van Ruusbroec' where you will learn all about the Sonian Forest. You also get a free map of the Sonian Forest with all hiking trails. You can also find this map in PDF on the website of the Sonian Forest:

www.zonienwoud.be

For those who find the Sonian Forest too far away for a day trip: there is a B&B near the beginning of the walk. For accommodation, you can also go to a hotel near Groenendaal train station.

www.hippo-droom.be

 

This walk is part of a series of high-level hikes in Flanders.

There is always a variant of +/- 12 km and one of +/- 20 km.

https://www.wandelpunt.be

 

 

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Route origin

Route description

Region

Statistics

Difficulty level: Hard (83/100)

Length: 20.5 km

Duration: 04h05


Total ascent: 186 m

Maximal slope: 4.08 %

Average slope: 0.91 %

Net ascent: 0 m

Total descent: 186 m

Difficulty level according to the author: 3/10

Roads and subsoil

Paved roads: 970 m (5 %)

Cobblestones: 0 m (0 %)

Scenery

Car free roads: 13.6 km (66 %)

Noise pollution

Amount of traffic


Natural area

Urban area

Water rich area

Characteristics

    Themes

      Groups

        Start and end of the route

        Closest address to start and end: Duboislaan 1, Hoeilaart, België

        Navigate to starting point

        Places of interest

        1. Parking Priory (50)

          0 · Parking

          This large car park, located between the Castle of Groenendael and the remains of the priory, …

          Sonian Forest
        2. Sonian Forest

          0 · Forest

          The Brussels painter René Stevens founded the oldest nature association in Belgium, linked to the …

          Pascal Brackman
        3. The Sonian Forest

          0 · Forest

          The Sonian Forest is the most important green space in the Brussels Region, the largest deciduous …

          Sonian Forest
        4. Tumulisite

          1 · Historical place

          Here we reach the ‘real’ ridge lines on our route, reaching an altitude of 130 m, the true summit …

          visit.brussels
        5. Vuylbeek

          0 · River

          The name of the river Vuylbeek ('Dirty brook'), which flows largely through the Sonian Forest, is …

          Sonian Forest
        6. Parking ISB (6)

          1 · Parking

          A very small car park, with only six spaces for cars, allowing access to the forest via the Drève …

          Sonian Forest
        7. Pond and springs in Tournay-Solvay Park

          1 · Source

          Along the pond that adorns the Tournay-Solvay Park, on the same side and just a few meters apart, …

          Coördinatie Zenne-Coordination Senne
        8. Tournay-Solvay Park and its castle

          0 · Park

          The Tournay-Solvay park bears the name of its former owners. This pretty estate with its …

          Sonian Forest
        9. Fagus - planted in 1806 - Bonnier II

          0 · Tree
          • genus: Fagus • height: 10 meter • circumference : 3,51 meter
          Sonian Forest
        10. Boitsfort/Bosvoorde Fietsenstalling f2

          0 · Bicycle shelter
          Type: Public Bicycle Parking Owner: NMBS Administrator: Stad/Gemeente
          Velopark.be
        11. Tournay-Solvay Park

          0 · Park

          Leaving the forest, let’s find out more about an illustrious Belgian family at the Tournay-Solvay …

          visit.brussels
        12. Parking Boitsfort station (30)

          1 · Parking

          Boitsfort station car park - there are around 30 parking spaces at the entrance to Tournay-Solvay …

          Sonian Forest
        13. Boitsfort/Bosvoorde railway station

          1 · Trainstation
          Boitsfort railway station is a railway station located in the municipality of Watermael-Boitsfort …
          Wikipedia
        14. Boitsfort/Bosvoorde Fietsenstalling f4

          0 · Bicycle shelter
          Type: Public Bicycle Parking Owner: NMBS Administrator: Stad/Gemeente
          Velopark.be
        15. Boitsfort Station

          0 · Trainstation

          Boitsfort station (Dutch: Station Bosvoorde) is a Belgian train station in Watermael-Boitsfort in …

          Sonian Forest
        16. Bicycle repair station

          1 · Air-pump

          This bicycle repair station, located in front of Boitsfort station, includes a pump and tools for …

          Sonian Forest
        17. Parking du Comte (20)

          1 · Parking

          This small car park can accept up to 20 cars, as well as 10 bicycles attached to rings by a chain. …

          Sonian Forest
        18. Enfants Noyés Nature Reserve

          0 · Lake
          The Enfants Noyés Nature Reserve is a nature reserve consisting of three large ponds located in a …
          Wikipedia
        19. Château de La Fougeraie

          0 · Castle
          The Château de La Fougeraie, also called the Château Wittouck, is a stately home in Belgium built …
          Wikipedia
        20. Fagus - planted in 1890 - Infante VII

          0 · Tree
          • genus: Fagus • height: 2 meter • circumference : 3,24 meter
          Sonian Forest
        21. Memorial to the Brussels attacks

          1 · Monument

          The memorial to the Brussels attacks in the Sonian Forest was built in response to the Brussels …

          Dromos
        22. Sonian Forest Railway

          0 · Historical building

          The Sonian Forest railway was a railway line between 1902 and 1920. It has since disappeared, …

          Sonian Forest
        23. Fagus - planted in 1760 - Saint-Hubert III

          0 · Tree
          • genus: Fagus • height: 10 meter • circumference : 3,89 meter
          Sonian Forest
        24. Foresters’ Memorial

          0 · Monument

          Just a stone’s throw from our route (about 200 m) you will find a very unusual mausoleum. It is …

          visit.brussels
        25. Picnic areas in the Sonian Forest

          0 · POI

          The picnic sites in the Sonian Forest all have the same forest furniture. This picnic area is one …

          Wandelpunt
        26. Impatiens parviflora DC.

          0 · Flower

          The Impatiens parviflora is a commonly naturalised escape from cultivation. It was first recorded …

          Pascal Brackman
        27. Zwaenepoel Forest Reserve

          0 · Natural area

          The Zwaenepoel is a UNESCO World Heritage Site. In Europe, beech forests are part of our natural, …

          Dromos
        28. Joseph Zwaenepoel Forest Reserve

          0 · Natural area

          The Joseph Zwaenepoel Forest Reserve (232 ha), in the Flemish Region, is one of the three integral …

          Sonian Forest
        29. Goose leg pond

          0 · Pond

          In the Sonian Forest, many ponds are named after their shape. This is the Gooseleg Pond: it has …

          Wandelpunt
        30. Arboretum Groenendaal

          0 · Arboretum
          The Arboretum of Groenendaal was founded in 1897, the year of the world exhibition that took place …
          Dromos
        31. Castle of Groenendaal

          0 · Castle
          The origins of the Augustinian priory of Groenedaal date back to 1343. From a hermitage, already …
          Dromos
        32. Groenendael Priory

          0 · Historical building

          In the heart of the Sonian Forest don’t miss the Groenendael Priory at node 43 (about 500 m), …

          visit.brussels
        33. Groenendaal Castle

          0 · Castle

          Next to the castle of Groenendaal there is the hip tarverne 'Sonian' where you can eat and drink …

          Wandelpunt

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        Activities

        Nearby

        Routes nearby

        Lodging nearby

        Services nearby

        Parking Priory (50)
        Sonian Forest
        The Sonian Forest
        Tumulisite
        Vuylbeek
        Parking ISB (6)
        Pond and springs in Tournay-Solvay Park
        Tournay-Solvay Park and its castle
        Fagus - planted in 1806 - Bonnier II
        Boitsfort/Bosvoorde Fietsenstalling f2
        Tournay-Solvay Park
        Parking Boitsfort station (30)
        Boitsfort/Bosvoorde railway station
        Boitsfort/Bosvoorde Fietsenstalling f4
        Boitsfort Station
        Bicycle repair station
        Parking du Comte (20)
        Enfants Noyés Nature Reserve
        Château de La Fougeraie
        Fagus - planted in 1890 - Infante VII
        Memorial to the Brussels attacks
        Sonian Forest Railway
        Fagus - planted in 1760 - Saint-Hubert III
        Foresters’ Memorial
        Picnic areas in the Sonian Forest
        Impatiens parviflora DC.
        Zwaenepoel Forest Reserve
        Joseph Zwaenepoel Forest Reserve
        Goose leg pond
        Arboretum Groenendaal
        Castle of Groenendaal
        Groenendael Priory
        Groenendaal Castle
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        PLUS
        200 m

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