In the Albani Diocesan Museum in Urbino.
The main image has Agnes with her attributes of lamb and palm branch, blond hair uncovered. In the scene to the left of her waist (see detail below) we see Aspasius with his sword and the fire that divided and consumed the onlookers.
This image in full resolution
More of St. Agnes
Photographed at the museum by Richard Stracke, shared under Attribution-NonCommercial-ShareAlike license.
Below: Detail of the martyrdom