St. Peter's Basilica took 120 years to build and went through a succession of architects who kept revising each other's plans.

Donato Bramante laid the first stone in 1506 with a Greek cross design inspired by the Pantheon, but Michelangelo changed it, then Carlo Maderno extended it into a Latin cross, and finally Gian Lorenzo Bernini spent 20 years decorating the interior with a team of over 200 craftsmen. The result is the world's largest church at 610 feet long, with a dome that weighs 14,000 tons supported by four pillars housing Christianity's most important relics: fragments of the True Cross, the lance that pierced Christ's side, and the Veil of Veronica.

Michelangelo carved the Pietà at 23, completing it in nine months from a single block of Carrara marble. After overhearing someone attribute it to another sculptor, he grabbed his chisel one night and signed his name across the Virgin's sash. It remains the only work he ever signed. Bernini's bronze Baldacchino above the papal altar consumed so much metal that Pope Urban VIII stripped the Pantheon's roof, prompting Romans to quip: "What the barbarians didn't do, the Barberini did."

VoiceMap's self-guided audio tours decode the basilica's layered construction, trace how Renaissance and Baroque masters competed to leave their mark on Christendom's greatest church, explain why Mary looks younger than Christ in the Pietà, identify the four pillars' hidden relics, and follow the Barberini bees swarming across Bernini's bronze columns.