The Monastery of Saint Nilus (Abbazia di San Nilo) in Grottaferrata was founded by Saint Nilus in the year 1004, at the exact spot where the Virgin Mary appeared to the saint and told him to found a church in her honor. The official name of the Abbey is Exarchic Greek Monastery of St. Mary of Grottaferrata.
Monastery of St. Nilus Grottaferrata
Useful information

Address: Corso del Popolo, 128, 00046 Grottaferrata. Phone: +39 06 9459309. Opening times: From 09:00 till 12:00 and from 15:30 till 19:00. Admission: Free.
History and curiosities
Before the abbey was built here it was the site of a Roman villa owned by Gregory, Count of Tusculum (and father of two Popes). The villa contained a former sepulchral monument, that had been converted, in the 4th century, into a Christian oratory and had iron window grates. These grates gave the city its name, Cryptoferrata, later to be changed to Grottaferrata.
Saint Nilus died the year after but the building was completed by a succession of abbots, the most notable being Saint Bartholomew and in 1024 the sanctuary was consecrated.
Many building materials were saved from the ruins of the former villa and incorporated into the new structure. These included marble columns, sections of cornice and blocks of the so-called perperino volcanic stone.
The good reputation of the abbey attracted many gifts and donations. The mosaics and parts of the former Cosmatesque decorations still testify to this.
From the 12th century onwards the abbey suffered from the incessant wars between factions in what are now the regions of Tuscany, Umbria and Latium.
In the 15th century the abbey became more important again and the castle was built, while the whole monastery was surrounded with fortifications (that still exist).
Famous artists such as Gian Lorenzo Bernini, who made the high altar in 1665, were commissioned to embellish the abbey. Antonio Sangallo the Younger was responsible for the portico, while Domenichino created the frescoes that can be seen in the chapel of St. Nilus and Annibale Carracci made the altarpiece depicting the “Madonna and Child with St. Nilus and St. Bartholomew”.
Unfortunately there is not much left of the original abbey church which was consecrated in 1024, except some mosaics portraying the 12 Apostles beside an empty (since Christ was on his way to heaven) throne.
The campanile stems from the 12th century.
One of the abbey’s main attractions is the famous library, where Leonardo’s “Codex Atlanticus” was conserved (in the Laboratorio di Restauro). It also houses writings by St. Nilus himself and an early 16th century print of Alvise Cadamosto’s collected travel writings.
Pope Benedict IX died and was buried inside the Abbey of Saint Nilus.