Captivated by the beauty of the panoramic views of the mountains and valleys of the Maiella visible from some points in the town, the poet Gabriele d'Annunzio nicknamed Guardiagrele 'la terrazza d'Abruzzo'' ("Abruzzo's terrace").
Guardiagrele is the seat of the Maiella National Park, and is part of the club "Borghi più belli d'Italia" (Most beautiful burghs in Italy).
The façade presents a splendid 14th-century gothic portal, among the most elegant in the Abruzzi Gothic style. The Coronation of the Virgin sculpture group in the portal lunette is also magnificent, attributed to the school of Nicola di Guardiagrele. Under the colonnaded portico, next to the lateral door, is the splendid fresco by Andrea De Litio (1473) portraying Saint Christopher. In the interior, completely rebuilt in the 18th century following an earthquake, crumbling stucco-work in the Baroque style and a shrine of the same period set off a 15th-century fresco representing the Madonna of the Milk.In addition to Santa Maria Maggiore, there are several other churches and palazzi or mansions of various ages which are of architectural interest, including La chiesa di S. Nicola di Bari (Founded in the 4th Century), Il Convento dei Cappuccini (1599), Palazzo De Lucia (16th century), Palazzo Elisii (15th-18h century), Chiostro del Palazzo Comunale Piazza San Francesco (17th century) .and Palazzo Marini (1391)
The patron saints of Guardiagrele are Saint Donatus of Arezzo and Saint Emidius. Annually between the 6th and 8th of August there is a festival celebrating these saints in which the effigy of Donatus is paraded around the streets of Guardiagrele. It is traditional to eat porchetta (oven or spit roasted suckling pig flavoured with pepper, rosemary, garlic and other seasonings) at this time.
In the 11th century Archimandrite Saint Nicholas the Greek led a group of monks fleeing the Saracens who had occupied Calabria. In 1338 his body was moved to Guardiagrele and interred in la Chiesa di San Francesco (14th century). His saint's day is celebrated on the third Sunday of May.