Original: Widor's best-known single piece for the organ is the final movement, Toccata, from his Symphony for Organ No. 5, which is often played as a recessional at wedding ceremonies and even at the close of the Christmas Midnight Mass at Saint Peter's Basilica (The Vatican City, Rome).
Simplified: The Toccata from his Symphony no 5 is one of the best known of all organ pieces, often played at the end of wedding ceremonies.