Soon a fierce persecution of Christians swept through Gaul, and many of the faithful were abused, tortured or put to death. Saint Denis, fearless of danger and heedless of his own old age, travelled among the Christians, visiting the prisoners and exhorting all to remain firm in their confession of Christ. Soon he himself was arrested along with several companions, and was tortured without pity. When he was publicly hung on a cross, he preached to the onlookers of the mystery of Christ's Passion. Taken back to prison, he celebrated the holy Eucharist for the last time, enveloped in a heavenly light. He and a host of other Martyrs were then beheaded on a hill -the highest point in the city- now called Montmartre [in Old French ‘mountain of martyrs] in their memory.
On this mountain - now the Parisian suburb of St. Denis - stands the 19th-century Church of Sacre-Coeur and the Basilica of Saint Denis. In this icon painting of the saint, notice two buildings in the two upper corners: Sacre-Couer and Saint-Denis.
There is a tradition that at his execution he rose up, took his own head in his hands, and walked for several miles to a place that later became the Basilica of St Denis in the town named after him. Before the French Revolution, the Kings and Queens of France were buried in this church.