Historic St. Peter’s Basilica in Vatican City took 120 years to complete. Almost 400 years later, visitors to the church can finally see every inch of its art-filled interior. The largest church in the world now boasts one of the world’s most innovative lighting systems.

Designed by significant Italian Renaissance artists like Michelangelo and Donato Bramante, St. Peter’s Basilica is a burial site for popes and a destination for Catholic pilgrims. Church tradition claims that St. Peter’s sits on the site where Peter, Jesus’ apostle, is buried.

The building has meaning for Protestants too. In the 1500s, funds to build St. Peter’s Basilica were raised by selling indulgences. Catholic doctrine at that time held that these “indulgences”—money paid to the church—could lessen or remove the punishment for sin.

Reformer Martin Luther fought this unbiblical practice. The Bible clearly teaches that Jesus Christ’s death is the only atonement for sin (John 14:6) and that salvation is a free gift. (Ephesians 2:8) In 1517, Luther railed and nailed against indulgences.

Luther’s “95 Theses” hammered onto the door of a Catholic church in Germany sparked the Protestant Reformation.

Luther shone a spiritual light on a dark church practice. Now lighting experts from OSRAM Licht AG, a global lighting manufacturer, are shining physical lights in St. Peter’s Basilica. Engineers worked for 18 months to install nearly 100,000 light-emitting diodes (LEDs) in the church.

The new lighting in St. Peter’s Basilica emphasizes the masterpieces inside the building. The church’s 27,000 yearly visitors can now view 10,000 square meters of mosaics (almost two football fields’ worth) in the formerly shadowy side aisles. Paintings that once disappeared in semi-darkness now shine in all their glory. An additional bonus? Visitors can read plaques and pamphlets without straining their eyes.

The digital lighting system allows specific lighting setups to be selected, created, or adapted. Want more light at the front and less on the sides? Or vice versa? The new system makes high-definition television image transmission possible too—with an energy savings of up to 90% compared to the old lighting.

“More than 500 years of history are now being bathed in digitally controlled LED light,” says OSRAM CEO Olaf Berlien. “The project demonstrates just how history and high tech can be combined in the best possible way.”