A very early computer, quite unlike any other, is discreetly hanging in the sacristy of a small chapel in the heart of Turin, the beautiful Italian city at the foot of the Alps. Thousands of people pass by every day along Via Garibaldi, one of the main shopping thoroughfares in town, but hardly anyone knows it is there. That is because the tiny baroque jewel that owns the artifact is hidden in plain sight, and the church only opens on Saturday afternoons and Sunday mornings for mass. Still, anyone in-the-know or curious enough to find it will be awestruck by the Perpetual Calendar of Giovanni Antonio Amedeo Plana.

Built by the astronomer and mathematician in 1831, the Perpetual Calendar took 10 years to complete, from planning to assembly. The device, which resides in the Chapel of Bankers and Merchants, operates via a simple wooden crank under the adorned golden frame, a crank that hides a stunningly accurate universal mechanical calculator spanning the years 1 to 4,000.