The Via Eremo delle Carceri runs ever more steeply from Assisi's Porta Cappuccini along the oak- and ilex-covered slopes of Mt. Subasio. Nestled at the head of a tree-smothered gorge 4km (2 1/2 miles) along the road, is the peacefully isolated Eremo delle Carceri (hermitage), built on the site where St. Francis often withdrew to meditate and pray with his followers. St. Francis started coming here in 1205 (when there was already a tiny Benedictine chapel), but the core of the buildings you see today were built in the early 15th century by St. Bernardino of Siena. The monks living here will sometimes show you around, but you are otherwise free to explore the public areas. You'll have to negotiate some tiny, rock-hewn passages to see the rocky bed where Francis slept, and a few worn frescoes in tiny chapels. Along a shady path, dramatic sculptures mark the site where Francis caused water to gush from the rocks, and beyond this a wooden cross and stone altar marking the spot where the saint preached his sermons to the birds.
The hermitage also makes a good starting point for walks in the woods, though the walk here along the road from Assisi is already fairly strenuous (you can drive and park here for free instead). Mt. Subasio is a protected regional park, and there are plenty of marked trails to follow. (Maps are available in town.)