Pietro Orioli, 'The Nativity with Saints', probably about 1485-95

The Christ Child, naked but with a gilded halo, lies on a bed of straw. Golden rays shoot out around him. A sparse timber frame with a thatched roof represents the stable where he was born; its beams rest on the rocky arch of a deep, dark cave which almost fills the background. The towers and roofs of Bethlehem rise on the left.

Kneeling around Christ in adoration are his parents, the Virgin Mary and Saint Joseph, with Saint John the Baptist on the left and Saint Jerome on the right. Standing at the sides are Saint Stephen (on the left) and Saint Nicholas of Bari (on the right). God the Father appears above, flanked by two angels, and blesses his son. Behind the Virgin are an ox and a donkey, which turns its rear to us, oblivious to the miraculous child in the manger. On the far left, behind Saint Stephen, the face of one of the shepherds is visible peering around the frame. The pilasters on either side of the main panel show, from top to bottom, the Annunciation to the Virgin; Saint Peter and Saint Paul; and Saint Francis of Assisi and Saint Lucy.

This large painting is the main panel of an altarpiece by Pietro Orioli. It is one of several versions that Orioli painted of this subject, and it demonstrates many of the stylistic features that made him one of the most important and influential painters in Siena in the last two decades of the fifteenth century. Unlike many his contemporaries, who clung to the decorative traditions of Sienese painting, Orioli was fascinated by perspective and naturalism. Here, he has set the sacred story in a believable landscape, with blue sky above and trees and buildings in the distance. The roof frame of the stable recedes along diagonals which, if extended, would converge at a single point behind the cave. The composition is carefully structured around an underlying geometry: the figures around Christ form a triangle, the apex of which is God the Father. A strong light falls on them from the left, giving an illusion of solid bodies under their clothes. The saints seem engaged in casual conversation, their variety of expressions and gestures very different from the graceful but more static figures of much contemporary Sienese painting.

The shape of altarpiece, with a single panel large enough to include the lateral saints normally separated in polyptychs, was one developed in the fifteenth century. This particular variant of a pala altarpiece, with a curved top, was first adopted by Orioli’s master, Matteo di Giovanni, for his Virgin and Child with Saints in the chapel of St Antony of Padua in Siena Cathedral. It was widely adopted and became the most popular format in Sienese territory in the late fifteenth century.