Microsoft and the Vatican build an AI digital twin of St. Peter's

If you've ever stepped inside St. Peter’s Basilica in Rome, you know the scale is almost impossible to wrap your head around. But looking at Michelangelo's dome from 400 feet below means you miss almost every tiny detail—including the 400-year-old pencil notes left on the walls by workers rappelling down ropes to clean mosaics.

Now, Microsoft and the Vatican have built an AI-powered digital twin of the world's largest church so anyone can inspect it millimeter by millimeter.

Half a million photos and 5,000 DVDs of data

The project was born back in 2022 when Microsoft President Brad Smith and Basilica Archpriest Cardinal Mauro Gambetti were admiring Michelangelo’s Pietà and began talking about how to make the cathedral accessible to people who could never make the trip to Rome.

To make it happen, Microsoft's AI for Good lab teamed up with Iconem, a French 3D digitization startup. In 2023, the team spent a full month inside the basilica flying two drones and deploying laser scanners and high-res cameras.

They captured nearly 500,000 ultra-high-resolution images, amassing 22 terabytes of data. To put that into perspective, burning that data would require nearly 5,000 DVDs. Stacked up, that pile would stand over 18 feet tall—about the height of a two-story building.

Smith noted that the advanced AI algorithms required to stitch that sea of pixels together into a seamless 3D model did not even exist two and a half years ago when conversations started.

A virtual tour and a structural checkup

The digital twin officially powers a suite of new experiences starting December 1, ahead of the 2025 Holy Year. A new website and app will offer virtual tours spanning from the roof down to St. Peter's tomb, along with audio guides and live queue tracking for the Holy Door.

In January, the model will also launch inside Minecraft Education, letting students worldwide explore the site.

On-site visitors will see two new immersive exhibits. One projects high-resolution images onto a rooftop dome, while another along an interior corridor showcases the basilica's construction history and workers' historical pencil scrawls.

Crucially, the scan doubles as an unprecedented conservation tool. AI scanning detected previously unseen structural cracks and missing tiles, giving preservation teams an exact blueprint for repairs before the church marks the 400th anniversary of its 1626 consecration.

Why it matters

We think this is one of the smartest demonstrations of tech diplomacy and practical AI Microsoft has pulled off in years.

For everyday people, it genuinely democratizes access to world heritage. Millions cannot afford a trip to Rome for the Holy Year, but anyone with a web browser—or kids playing Minecraft—can now explore artifacts with better visibility than an on-site tourist squinting through dim lighting.

For historic preservation, it sets a completely new operational standard. Instead of erecting hazardous scaffolding and risking human lives to visually inspect hundreds of feet of stone, drones and computer vision can locate micro-cracks in days.

The elephant in the room is cost and scalability. Digitizing St. Peter’s Basilica took weeks of drone flights, 22 terabytes of high-end scanning, and custom AI pipelines backed by a trillion-dollar company. Most endangered heritage sites around the globe don't have Microsoft footing the bill. Still, proving this level of structural AI analysis is possible lays down a challenge that hardware and software makers will race to make cheaper.