Pedro Duque Cornejo
St. John on Patmos
Choir stalls, Cáceres Cathedral, Cáceres, Spain
Most images of this type have the saint in the lower right gazing upwards at the upper left, where heavenly light or some other symbol reflects Revelation 1:1, "The Revelation of Jesus Christ, which God gave unto him, to make known to his servants the things which must shortly come to pass: and signified, sending by his angel to his servant John." But in other works the artist chooses to fill the upper left with images drawn from Revelation itself. In this case, John is recording his vision of Revelation 12:1-9, with the "woman clothed with the sun," the archangel Michael, and the dragon with seven heads.
It is not clear why there are wings on the woman, whose description is conventionally applied to Mary as Immaculate Conception.
Many images are like this one in adding John's attribute, an eagle.
This image in full resolution
More of St. John the Evangelist
More of the Immaculate Conception
Photographed at the cathedral by Richard Stracke, shared under Attribution-NonCommercial-ShareAlike license.