AENEAS . SILVIVS . PICCOLOMINEVS . NATVS . EST . PATRE
SILVIO . MATRE . VICTORIA . XVIII . OCTOBR .
MCCCCV . CORSIANI . IN . FVNDIS . GENTILITIIS . BA-
SILEAM . AD . CONCILIVM . CONTENDENS . VI . TEM-
PESTATIS . IN . LIBYAM . PROPELLITVR.

The person who brings you my letter is a youth of
Siena, by name ./Eneas Silvius, of an honorable family,
and very dear to me, not only because he has followed
my teaching for two years, but also by reason of
the keenness of his intellect, and his graceful style; his
manners also are polite and cultured.

The Piccolomini Library, incorporated into the northwest side of Siena Cathedral houses precious illuminated choir books and frescoes painted by Pinturicchio, probably based on designs by Raphael. The frescoes tell the story of the life of Siena's favourite son, cardinal Enea Silvio Piccolomini, who eventually became Pope Pius II. He was the uncle of cardinal Francesco Todeschini Piccolomini. The frescoes depict ten remarkable events from the secular and religious career of Pope Pius II, first as a high prelate, then bishop, a cardinal and ultimately pope.

Each scene is labelled with a Latin inscription, taken from the pope’s biography by the humanist writer Giovanni Antonio Campano and the Commentaries written by Enea Silvio himself. The story begins at the end of the room next to the right-hand window, then proceeds clockwise around the room.

Enea Silvio Piccolomini leaves for the Council of Basel

The elegant knight at the center of the composition, who turns towards the viewer, is the twenty-six year old Enea Silvio. The troubles of departure for the council of Basel are recalled in the Commentaries, citing the storm that caught his ship between the island of Elba and Corsica, diverting it to the south. These events are announced in the dark cloud on the left, but the rainbow also recalls the successful landing, between Porto Venere and Genoa, and the serene return.[3].

Wearing a splendid travelling cloak, a fur collar, and a pilgrim's hat, the young man sits on a white horse - an obvious allusion to his future stature, for white horses, were reserved for popes.

Rare is the description of an atmospheric event in Italian Renaissance painting, dictated here by narrative requirements, which was resolved with large black clouds that fray, in the form of invisible rain, to the sea, illuminated by the golden glimmerings of lightning. A similar effect is found in the fresco of the Red Sea Passage in the Sistine Chapel. The effect that the storm has on the ships is well represented on the left side, while the right one is dominated, by contrast, by the clear weather and the pleasant view of a walled city.
The ride, which leads to the right, shows a great variety of figures and characters, both in clothes and in attitudes; the choice of characters, which had to be inspired by the iconographic tradition of the cavalcades of the Magi, shows both knights and people on foot, and numerous signs of the rank of each: from the clothes of a cardinal, to the halberdier from behind with his gaudy clothes, from the knight of left holding a greyhound on a leash, the exotic white horse with long ears, up to a curious traveler with a bandaged face and a sort of umbrella for a hat [3].

For this scene there are Raphael's preparatory drawings, especially with regard to the ride [3].