1. The Dome. Opened on November 6 of 1622, it is pure design and chosen work by Carlo Maderno. Measure: 16.61m. in diameter and 71.76m. from the floor of the basilica to where is placed the cross with the bronze star. After st. Peter’s Dome, this is the greatest in Rome. Externally it rises above an octagonal drum where columns with Ionic capitals support a cornice making an amazing harmony with the windows, these are placed below alternately triangular and curvilinear tympanums. Above a second frame is set the vault, divided by strictly thinned ribs, among which there are eight blind windows with angular and curved lines and, upwards, eight round windows with shells on top. The lantern also has as many windows, long and narrow, separated by double columns. With Refined originality are made the capitals of the columns a special order, because in each of the twin columns there are a cherubyn top that forms with his wings an swirl. They are work of Borromini, who in 1621 worked as a stonecutter with Maderno.
2. The fresco by Giovanni Lanfranco. Inside, the dome rests on the four powerful cruise pylons and the arches that connect them, forming four triangular pendetives on which the round frame of the drum rests. There is a golden background, in mosaic is written:
ANDREAS CHRISTI FAMULUS GERMANUS PETRI AND IN PASSION SOCIUS.
The drum divided by double fluted pillars, among which the windows open, with no sculptural decoration. At the top is the famous fresco of Lanfranco, already related to Domenichino, executed from August 4, 1626st 4, 1626
English: World English Bible - WEB
WP-Bible plugin to February 9, 1628, depicting the “Glory of Heaven” in which the Virgin Assumed, from the throne of angel-like clouds turn high where Christ waits for hem. S. Andrew Apostle presents to the Salvatore his homonymous Andrew Avellino, kneeled. On the other hand, s. Peter recommends st. Cajeano Thiene. There are Adam and Eve and many more Saints. Around, the choirs of the holy Fathers, the Prophets, the Martyrs, the Virgins, the Cherubs, ascend to the light where Christ reigns. “One of the highest moments in the history of the art is the decoration of the cupola of the church of Sant’Andrea della Valle, performed by Giovanni Lanfranco. In the cupola, the painter, who arrived from Parma and raised in the school of Annibale Carracci, realized, between 1623 and 1628, his masterpiece and the first example of Baroque illusionism, bringing the sky into the church, thanks to a swirling motion of the Figures hovered in the air and a strong vibration of light that enlightens in golden tones and gives the spectator the feeling of a static abduction. “(Lauretta Colonnelli, in Il Corriere della Sera, March 16 of 2002, 57)
3. The pendentives of Domenichino. Performed in the period from December 1622 to February 1628, where Domenichino also pinted the fresco of the vault of the apse, these four pendetives contain, with great compositional harmony, the four Evangelists. st. Mattew, thinking giant, leaning in his legs, his chin on his hand, holds his book on his left side against his side. Also an angel (symbol of the evangelist) supports the cross; Another points out a straight table holder by another little angel; A third, under st. Mattew’s feet, rolls a roll around a cradle. St. John Evangelist, an young man in ecstasy, sits on the clouds, riding the eagle (symbol of the evangelist) and to the right an angel holds the book on which it is about to write, while another on the opposite side offers him the pen and inkwell. A putto holds him the torch and Below, two others embrace each other. St. Luke is an old bearded man wrapped in a large cloak sited on the back of the bull (symbol of the evangelist),who, with two hands carries a scroll where FUIT SACERDOS is written. To the right an angel shows the portrait of Our Lady; Below, two others hold the miter and the priestly baldric. St. Mark, an absorbed old man, his torso placed on his legs, sitting three-quarters turn on the left, with a large fleece around the bust, reads on a table. To the left there is the angel with the white-red checked flag ; Below is the lion (symbol of the evangelist). The merits of the Master, converted in mistakes by the foes, were appreciated and exalted by the poster who came up on the cornice of the vault to study and copy the originals more closely. Testimony of this are the numerous signatures, inscriptions or graffiti, marked on the drum plaster as far as it can be reached by the artists, by Ottaviano Caroselli inventoried in 1907. Among those reported by Caroselli we add the signature of the Goya, randomly discovered on April 15, 1999 from p. Francesco Gil Alvarez, C. R.