Boniface IV was a Benedictine monk-disciple of St. Gregory the Great whom he succeeded at one remove in the papacy. His most enduring act was to obtain from the Emperor Phocas in 609 the great Pantheon of Agrippa — the magnificent Roman temple to all the gods — and to consecrate it as a Christian church, Santa Maria ad Martyres ('St. Mary and All the Martyrs').
Twenty-eight cartloads of martyrs' bones were translated from the catacombs into the new church for the consecration. The Pantheon became the first temple of pagan Rome to be converted into a Christian church and is the only surviving ancient Roman temple in continuous use to this day — its survival into the modern world is the direct fruit of Boniface's act of consecration.
The dedication established the Feast of All Saints (originally May 13, later moved to November 1) in the Roman calendar — the origin of the great solemnity that still anchors the autumn of the liturgical year.