The Certosa di Trisulti is a monastery surrounded by centuries-old oak woods founded in 1204 by the will of Pope Innocent III and entrusted since 1208 to the Carthusian monks from which the name "Certosa" derives. The name Trisulti derives from the Latin tres saltibus which is the name by which it was called a 12th century castle managed by the Colonna and which dominated the three passes that led respectively to Abruzzo, Rome and the southern area of the Papal States. . To enter the Charterhouse, enclosed by walls, one must cross the large portal surmounted by a bust of San Bartolomeo, the work of Jacopo Lo Duca, a pupil of Michelangelo Buonarroti. In the main square there is the ancient Romanesque-Gothic guesthouse called "Palazzo di Innocenzo III", which houses an ancient library of 36,000 volumes and the church of San Bartolomeo. The ancient pharmacy of the monastery, from the 18th century, is made up of various rooms on two levels; it is decorated with realistic Pompeian-inspired trompe-l'œil and features eighteenth-century furnishings. In the pharmacy you can see the jars in which the medicinal herbs and poisons extracted from snakes were kept. The garden in front of the pharmacy is interesting, where the box hedges reproduce animal shapes: once it was the botanical garden.