The Pantheon, built originally in 27 B.C. and rebuilt by the Emperor Hadrian c. 126 A.D. to honor pagan Roman gods, was consecrated by Pope Boniface VI and dedicated to the Blessed Virgin Mary and All Martyrs ca. 609, thus beginning the commemoration of All Saints.
O Almighty God, who hast knit together thine elect in one communion and fellowship in the mystical body of thy Son Christ our Lord: Grant us grace so to follow thy blessed saints in all virtuous and godly living, that we may come to those ineffable joys which thou hast prepared for those who unfeignedly love thee; through the same Jesus Christ our Lord, who with thee and the Holy Spirit liveth and reigneth, one God, in glory everlasting. Amen.