Along the eastern side of the Basilica, a side door gives access to the majestic crypt that extends below the church along its entire surface. A vestibule leads to the burial ground of the Petrucci family, a room with brick columns and cross vaults, with the dominating funeral monument of Celia Petrucci (who died at fifteen years of age in 1558) consisting of a large travertine arch inserted in a classical-style architectural structure. A few steps below, to the right, is the entrance to the crypt: covered by large lowered cross vaults, it is characterized by its orientation which is opposite to that of the church above. Here are the tombs of famous Sienese families and artists such as Francesco di Giorgio Martini and Giacomo Cozzarelli. Girolamo di Benvenuto’s fresco The Last Judgement, which is now displayed in the friary museum after being relocated there in 1910, once occupied the bottom wall and, together with the tombstones and dusky light, was to favour meditation and evoke the mystery of death.