Though overshadowed by the ornate Basilica Notre Dame, the Romanesque-Gothic beauty of the Cathedrale St Jean is the more ancient and important of Lyon's lovely churches. At the heart of Old Lyon, it is the home of the Primatiale of the Gauls, supreme over all the archbishops of France. The title was granted in 1079, though it is now largely symbolic.
The angular facade, begun in 1175 and completed in 1476, opens onto a far more extravagant interior, with several soaring chapels, stained glass dating to the 1300s, and most famously, the 1598 astronomical clock. Saint John's most noted attraction can calculate religious dates (such as Easter) until 2019, as well as the positions of stars above Lyon. But you're really here to see it in motion, complete with mechanical bell ringers and roosters.
At the heart of Old Lyon, the ancient Cathedrale St Jean can be reached on the Metro D line, Vieux Lyon-St. Jean. Be sure to show up at noon, 2 p.m. or 3 p.m. to see the astronomical clock chime.
Next door, the 11th-century Manécanterie (Choir School) may be the oldest extant building in Lyon; it's free to visit and open daily.