This extremely rare cartoon by Fabrizio Castello is for an oval fresco with the allegorical figure of Pietas, inserted in the centre part of a vaulted triangle between the semi lunettes with the prophets Daniel and Elias in the elaborate decoration of the Lower Prioral cell (Celda Prioral Baja) in the Monastery of San Lorenzo in the Escorial, executed by Francesco da Urbino and assistants. Datable to 1581-82, this is one of the most interesting and harmonious ensembles in the Escorial. The intense decorative program of these rooms as well as the entire renovation of the building was commissioned and closely supervised by King Philip II and his assistants. The date of 1581 appears in Roman numerals on the base of the throne of King Solomon, in the central scene of the vaulted ceiling, depicting the Judgement of Solomon. Several preparatory studies have survived for this room, the majority by Francesco da Urbino (1545-1582), a native of Borgo San Sepolcro, who had arrived in Spain in 1569 (see Literature).

García-Frías Checa and García-Toraño Martínes, in their article on the drawings by Francesco da Urbino related to this decoration (loc. cit.), have suggested on stylistic grounds that the present cartoon is actually the work of the Genoese artist, Fabrizio Castello, a very skillful assistant of Francesco da Urbino, who according to both scholars was most probably responsible for the allegorical figures and their preparatory studies. In fact, the present sheet is executed with a more robust and vigorous use of the pen, when compared to other sheets by Francesco da Urbino, which are characterized by more delicate lines. It is documented that Fabrizio Castello received regular payments for this work.

The present cartoon, first related to the decoration of the El Escorial by Dr. Zahira Véliz, former curator of the Apelles collects ion, is a very rare survival and an important testimony of the Genoese cantieri in the monumental project headed by Giovanni Battista Castello, il Bergamasco (1509-1569).