Opposite the _Cappella del Voto_ is the Chapel of the Baptist in the left transept. It contains, in a richly worked reliquary, what is supposed to be one of the arms of the Baptist himself, which Pius II. presented to Siena in 1464. The chapel was built by Giovanni di Stefano, the external marble decorations being by Lorenzo di Mariano. Of the two pedestals that support the marble columns at the entrance, the one on the right is a genuine antique, which Antonio Federighi bought in exchange for a pair of oxen, and the one on the left is his own imitation of it.[84] Within, the presiding genius of the place is Donatello's St John in bronze, one of the master's latest works, full of dramatic expression and the same spirit of austere prophecy that we found in the Magdalene of the Florentine Baptistery. The marble statues of St Ansanus and St Catherine of Alexandria are by Giovanni di Stefano and Neroccio respectively; the latter, assigned to the sculptor in 1487, was left unfinished at his death. The bas-reliefs of the Font--representing scenes from Genesis, and two of the labours of Hercules--are fine and characteristic works of the school of Giacomo della Quercia, and should perhaps be ascribed to Antonio Federighi. The eight frescoes were originally executed by Pinturicchio and his pupils, between 1501 and 1504, for Alberto Aringhieri. On the left and right of the entrance, by Pinturicchio himself, we see Alberto in youth and age; first as a young knight keeping vigil, then advanced in years, kneeling in prayer, in the dress of a knight of Rhodes; they are full of charm, especially the first, in its harmonies of grey and red, the highest expression of Sienese chivalry:-- "Unfathomable thoughts with him remain Of that great bond he may no more eschew, Nor can he say, 'I'll hide me from this chain.'"[85] The fresco opposite, representing the Birth of the Precursor, is also from Pinturicchio's hand. Appropriately placed above the two portraits of Alberto are the Vigil of St John and his Preaching in the Wilderness; they are very naive and charming, with odd formal trees and landscape against the gold background, and are ascribed by Mr Berenson to Baldassare Peruzzi, of whom there is documentary evidence that he worked here in 1501; they would thus be very early works of his, of the same period as they are in the same style as the little Madonna in the Accademia. These four frescoes have been repainted. The three that remain have been entirely replaced by later work; the Baptism of Christ and the Martyrdom of the Baptist, painted by Francesco Rustici at the beginning of the seventeenth century, the Saint in Prison, by a modern artist, Cesare Maccari.