Civita Castellana sits on an isolated tufa plateau, and the gorge of the Rio Maggiore that carves around three sides of it is as much a defining feature of the town as any building. The ravine drops sharply from the plateau edge — in places 30 metres or more — and the tufa cliffs glow orange and ochre in afternoon light. Walking paths descend from the town into the gorge, where the vegetation is dense and the temperature noticeably cooler than above. The gorge provided the town's natural defence for millennia before any wall was built, and the Faliscans sited their city here precisely because the plateau was so easily held.
The paths are not well signed but are easy enough to follow; the main descent is near the northern edge of town, not far from the Forte Sangallo. The walk along the floor of the gorge takes around an hour end-to-end. The tufa walls are streaked with lichen and draped with ferns, and in spring the floor is thick with wildflowers. It is a genuinely wild piece of landscape minutes from the town centre, and almost entirely ignored by visitors.