San Silvestro, Viterbo

San Silvestro is a Romanesque-style, Roman Catholic parish church located at the intersection of Via dei Pellegrini #23 with Piazza del Gesu, in Viterbo, region of Lazio, Italy. It is also known as Chiesa del Gesù, since it was previously administered by the Jesuits. The church is infamous for being the site of the murder of Henry of Almain by his cousins Simon and Guy de Montfort: a murder occurring during a mass in 1271 attended by cardinals and kings.

Source: Wikipedia