Rome's largest Jesuit church, this 17th-century landmark harbors some of the most city's magnificent trompe-l'oeil. To get the full effect of the marvelous illusionistic ceiling by priest-artist Andrea Pozzo, stand on the small disk set into the floor of the nave. The heavenly vision above you, seemingly extending upward almost indefinitely, represents the Allegory of the Missionary Work of the Jesuits and is part of Pozzo's cycle of works in this church exalting the early history of the Jesuit Order, whose founder was the reformer Ignatius of Loyola. The saint soars heavenward, supported by a cast of thousands; not far behind is Saint Francis Xavier, apostle of the Indies, leading a crowd of Eastern converts; a bare-breasted, spear-wielding America in American Indian headdress rides a jaguar; Europe with crown and scepter sits serene on a heftily rumped horse; while a splendid Africa with gold tiara perches on a lucky crocodile. The artist repeated this illusionist technique, so popular in the late 17th century, in the false dome, which is actually a flat canvas—a trompe l'oeil trick used when the budget drained dry. The overall effect of the frescoes is dazzling (be sure to have coins handy for the machine that switches on the lights) and was fully intended to rival that produced by Baciccia in the nearby mother church of Il Gesù. Scattered around the nave are several awe-inspiring altars; their soaring columns, gold-on-gold decoration, and gilded statues make these the last word in splendor. The church is often host to concerts of sacred music performed by choirs from all over the world. Look for posters at the church doors for more information.