The Cathédrale Saint-Pierre dominates the Vieille Ville from its hilltop position, the old town's highest point. The current structure began in 1150 and took over 150 years to complete, which explains its architectural inconsistency: Romanesque nave, Gothic choir, and a Classical portico added in 1750 that looks like it belongs to a different building. Calvin stripped the interior of Catholic decoration in 1535, leaving a sober Protestant space that still feels notably bare by the standards of comparable medieval cathedrals.
The north tower is open to visitors and worth climbing for a good view over the old town and the lake. Below the cathedral, the Site Archéologique de Saint-Pierre preserves the multi-layered remains of earlier buildings on the site, including intricate 5th-century mosaics. The Auditoire de Calvin, a chapel immediately adjacent, was where John Knox preached to English and Scottish Protestant exiles in the 1550s — it is here that the Geneva Bible (the first mass-produced English Bible for household use) was produced.