The Flight into Egypt
Convent Church of St. John the Baptist, Müstair, Switzerland
Mary's mount is not an ass but a horse. Behind the horse is one of the boys that the Gospel of Pseudo-Matthew says accompanied Joseph and Mary on the journey. He carries a large duffel bag on his shoulder (chapter 18). Compare the satchel carried by the man in
a Croatian relief
from a century and a half later.
Joseph holds a lead attached to the horse's bridle. Behind him is a stylized city with walls, tower, and buildings. The arch behind the horse probably represents the city's gate. Since Jesus and Joseph are both pointing away from the city we may presume that it is Bethlehem.
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Photographed at the church by Richard Stracke, shared under Attribution-NonCommercial-ShareAlike license.