Named for the city of Gubbio, Umbria, Italy. Dating from the Umbrian civilization in the 7th century B.C., Gubbio flourished in the Middle Ages and is one of the best-preserved Italian medieval cities. It was on a hill above the city that geologist Walter Alvarez {see planet  (3581)} found an iridium-rich layer originating at the transition between the Cretaceous and Tertiary periods. His father, Luis Alvarez, physicist and Nobel laureate, interpreted the layer’s presence as the result of a catastrophic impact of an asteroid with the earth. Gubbio is also famous for the story of St. Francis and the wolf, and for St. Francis’ “Ceri Marathon”. (M 22247) _ _.