Silva Carbonaria

Silva Carbonaria, the "charcoal forest", was the dense old-growth forest of beech and oak that formed a natural boundary during the Late Iron Age through Roman times into the Early Middle Ages across what is now Belgium. The forest naturally thinned out in the open sandy stretches to the north and formed a barrier—trackless to the outsider—on the heavier soils to the south. Yet further to the south, the higher elevation and deep river valleys were covered by the even less penetrable ancient Arduenna Silva, the deeply folded Ardennes, which are still forested to this day. The Silva Carbonaria was a vast forest that stretched from the rivers Senne and the Dijle in the north to the Sambre in the south. To the east Silva Carbonaria extended to the Rhine, where near Cologne in 388 CE the magistri militum praesentalis Nannienus and Quintinus counter-attacked a Frankish incursion across the Rhine in the Silva Carbonaria. Its northern outliers reached the then marshy site of modern Brussels.