The beeches in the Sonian Forest grow so tall and straight that people call it the cathedral forest, and once you stand under them on a misty autumn morning the name stops sounding like tourist talk. This great woodland on the southeastern edge of Brussels covers thousands of hectares, and most of the famous columns of grey trunks were planted in the late eighteenth century, when the Austrian Habsburgs ruled these lands and their foresters reshaped the old wood. A few patches, including the Tict reserve near La Hulpe and Waterloo, are left to grow wild with no felling at all, and they form part of the UNESCO listing for the ancient and primeval beech forests of Europe, a chain of reserves stretching across the continent.
In the strict reserves, dead trees are left where they fall, and that is precisely the point: rotting wood feeds beetles, fungi, woodpeckers and bats, and the forest slowly rebuilds itself the way it did before anyone managed it. Paths run along the edges, and the light that filters through the canopy in May, bright green and soft, is worth the trip alone.
This is not a riding destination in itself. The forest is crossed by the Brussels ring road and a few main roads with heavy commuter traffic, and the forest lanes are for walkers, horses and cyclists. Treat it as a pause: park at one of the forest entrances, walk twenty minutes into the trees, and let the noise drop away. The roads south of here, into Walloon Brabant, become quieter and more rolling, with farmland, castle farms and small villages, and the Ardennes are less than two hours away for real curves.
Waterloo, three kilometres away, has fuel, cafés and everything practical, and of course the battlefield where Napoleon met his end in 1815, with the Lion's Mound, a vast artificial hill topped by a cast-iron lion, the panorama painting and the memorial museum. La Hulpe has a lovely château park, and Hoeilaart, on the Flemish side, was once famous for growing grapes in heated glasshouses. Belgian waffles and a strong local beer on a terrace make a fine end to the walk.