The Sonian Forest is the great beech woodland on Brussels' south-eastern edge, a remnant of the ancient Silva Carbonaria and part of a UNESCO-listed group of primeval beech forests. It is a strong half-day escape from the city, with marked paths for walking, running and cycling through ponds, old droveways and tall 18th-century beech stands.
Camping and fishing are not allowed, so come for the trails rather than facilities.