Sentence:  The decoration of a <WSD>lunette</WSD> discovered in the Duomo of Pistoia in the 1950s, which represents Christ blessing and Saints James and John, all bust-length, constitutes a more remarkable and stylistically more advanced approach to painting. 
Meaning of the word marked with <WSD> tags:  A crescent-shaped recess or void in the space above a window or door. (from 18th c.)