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Rare first state of this separately issued seventeenth-century engraving, illustrating the newly arranged Vatican grottoes beneath St Peter’s Basilica.

This map was engraved by Pietro Paolo Drei after drawings prepared by his father, Benedetto Drei, both of whom served as fattori (site superintendents) for the Reverenda Fabbrica di San Pietro. Their responsibilities placed them at the center of project, just as the subterranean chapels, stairways, and viewing shafts were being laid out around the Apostle’s tomb.

The map presents a carefully measured ground plan. New architectural elements—radiating chapels, access stairwells, and oculi that admit light from the basilica floor—are shown in strong outline, while the positions of ancient burials are marked individually: some are identified by name, others labelled ignoto, and a few rendered as skeletal remains or linen-wrapped bodies. Notes point out archaeological finds such as a heap of earth that yielded Constantinian coins and a pile of bones transferred from the old basilica. A long inscription at left recounts the drawing’s purpose; at right, Benedetto dedicates the image to Cardinal Francesco Barberini.

The grottoes themselves had been largely cleared by 1600 yet remained little used until Paul V (1605–23) provided a coherent circulation scheme, adding two stairways and several chapels (1616–17). Under Urban VIII (1623–44), Bernini inserted four oratories in the pier foundations and connected them to the main floor, giving the crypt a defined liturgical function. Throughout these campaigns the Drei family advanced within the Fabbrica’s technical staff—Benedetto from trench digger to fattore, Pietro Paolo from survey assistant to his father’s successor—ensuring a continuous, expertly informed stewardship of St Peter’s building history during a period of rapid change. 

States of the Engraving / Rarity

The engraving was first issued in 1635 to accompany (though not to be bound into) Francesco Maria Torrigio’s Le sacre grotte vaticane, the earliest printed description of the excavations. Subsequent work for the foundations of Bernini’s baldacchino soon rendered the image incomplete, so Pietro Paolo re-worked the copper around 1638–39, adding the new chapels within the four great crossing piers and other discoveries made in 1626.

The revised impression retains Benedetto’s original date but bears the imprint of Giovanni Giacomo de Rossi, who assumed control of the family press after 1639; surviving examples of either state are exceptionally scarce.