The Iron Crown is so called from a narrow band of iron about one centimeter (three-eighths of an inch) within it, said to be beaten out of one of the nails used at the crucifixion. According to tradition, the nail was first given to Emperor Constantine I by his mother Helena, who discovered the cross of the Crucifixion.
How it fell into the hands of the Lombard kings, Germanic conquerors of northern Italy, is not well explained. Theodelinda, the queen of Lombards who resided at Monza in the late sixth century, in many legends is said to have been involved in its discovery.
Some scholars posit that there were, in fact, many Holy Nails being circulated at the time. Almost thirty European countries lay claim to a holy nail . Constantinople seems to have made liberal use of them: "Empress Helena, who seems to have spent much of her reign locating holy relics, once cast a nail from the Holy Cross into the sea to calm a storm. Another was fitted to the head of a statue of the Emperor Constantine, while a third was incorporated into his helmet ." A fourth nail was melted down and molded into a bit for his horse.
In how the nail in the Iron Crown in particular reached the Lombards: "Constantine also understood the value of these objects in diplomacy ." Several were sent off to various dignitaries, one of whom was Princess Theodolina. "She used her nail as part of her crown, the famous Iron Crown of Lombardy ." This was said to have been given to her by Pope St. Gregory the Great for her part in converting the Lombards to catholicism. She later donated the crown to the Italian church at Monza in 628, where it is preserved as a holy relic. It was later used in Charlemagne's coronation. The crown became one of the symbols of the Kingdom of Lombards and later of the medieval Kingdom of Italy.
The outer circlet of the crown is of six gold and enamel segments of beaten gold, joined together by hinges and set with precious stones that stand out in relief, in the form of crosses and flowers. Its small size and hinged construction have suggested to some that it was originally a large armlet or perhaps a votive crown. Probably the little size of the crown was caused by a readjustment after the loss of two segments, as proven in historical documents.
On May 26, 1805, Napoleon Bonaparte had himself crowned King of Italy at Milan, with suitable splendour and magnificence. Seated upon a superb throne, he was invested with the usual insignia of royalty by the Cardinal Archbishop of Milan, and ascending the altar, he took the iron crown, and placing it on his head, exclaimed, being part of the ceremony used at the enthronement of the Lombard kings, Dieu me la donne, gare à qui la touche – "God gives it to me, beware those who touch it". Bonaparte would use it as the first step in creating an empire.
On the occasion, Napoleon founded the Order of the Iron Crown, on June 15, 1805. After Napoleon's fall and the annexation of Lombardy to Austria, the order was re-instituted by the Austrian Emperor Francis I, on January 1, 1816.
After the war between Austria and Italy, when the Austrians had to withdraw from Lombardy in 1859, the Iron Crown was moved to Vienna, where it remained until 1866 when it was given back to Italy after the Third Italian War of Independence.
A surprising image of the Iron Crown figures in Chaper 37 "Sunset" of Herman Melville's Moby-Dick. The brief chapter is devoted to Captain Ahab's soliloquy. Among his delusions of persecution and of grandeur, he imagines himself crowned with the Iron Crown of Lombardy.