At the beginning it was a small chapel dedicated to the martyrs Hadrian and Natalia. In 1131 it was enlarged and dedicated to Saint Nilus and Saint Bartholomaeus, and their relics were venerated there. In 1610 Cardinal Odoardo Farnese had it decorated and frescoed by Domenichino.

At the back, to the left, St. Nilus prays before the Crucifix to be delivered from a temptation and Christ is represented blessing him. It is the fresco which better depicts the contemplative spirit of the Saint, who passed so many hours of the day and night in prayer.

In the middle, the meeting of St. Nilus with the Emperor Otto III, near Gaeta. It was on that occasion that Otto said to Nilus "Ask me all you wish and I will give it to you". The saint answered: "I ask you only for your soul, because you also will die and will have to give a strict account of your life to God". Here we can observe many portraits: the emperor is the Cardinal Odoardo Farnese; the man holding the horse's reins is the self-portrait of Domenichino, the person near him, with the elbow on the horse is Guido Reni, then man near him seen in profile is Guercino with the lance.

On the left of the altar there is the scene of the healing of a possessed young boy, a miracle obtained by St. Nilus by his prayers.

On the altar a painting of Annibale Carracci depicts the Virgin between the two founders.

On the right wall, again, the apparition of the Virgin to the two Saints.

Then, at the center, the Church's Construction, and St. Bartholomaeus looking at the project with the architect (portrait of Annibale Carracci).

At the back Domenichino's interpretation of the miracle of the column. During the construction works, a column was running along a slope. The hemp ropes to pull it broke and the column was falling on a monk. St. Bartholomaeus with his prayer stopped it.

In the background, on the left, St. Bartholomaeus stops a terrible storm which would have ruined all the harvest. The farmers, desperate, began to curse. The saint, full of comprehension for their problems, prays and the weather clears up again. It is the symbol of the concrete charity of the saint for his brothers. It was he who gave to the farmers the land of Grottaferrata received in gift from the counts of Tuscolo.

Four columns of dark African marble delimitate the presbytery. On the altar stands a magnificent bronze tabernacle, previously placed on the main altar. The ceiling is in blue lacunars with gold ornaments.