In around 1205 St Francis chose these caves above Assisi as his hermitage where he could retire to contemplate spiritual matters and be at one with nature. The carceri (isolated places, or 'prisons') along Monte Subasio's forested slopes are as peaceful today as in St Francis' time, even though they're now surrounded by various religious buildings.
Take a contemplative walk or picnic under the oaks. It's a 4km drive (or walk) east of Assisi, and a dozen nearby hiking trails are well signposted.
