First a Celtic settlement, then a Roman market town, Speyer gained prominence in the Middle Ages under the Salian emperors, hosting 50 imperial parliament sessions (1294–1570).
In 1076, the king and later Holy Roman Emperor Heinrich IV, having been excommunicated by Pope Gregory VII, launched his penitence walk to Canossa in Italy from Speyer. He crossed the Alps in the middle of winter, an action that warmed the heart of the pope, who revoked his excommunication. He lies buried in the Kaiserdom.
In 1529, pro-Luther princes ‘protested’ a harsh anti-Luther edict issued by the Diet of Speyer, thereby starting the use of the term ‘Protestant’.