The first apparitions of the archangel Michael in Western Europe were granted to the Bishop of Sipontum (rebuilt in 1256 as Manfredonia), in Apulia. Three times the Archangel appeared, nightly, the last time on September 29, 493, the bishop reported. The Archangel indicated the transformation into a Christian church of a grotto sacred to Mithras, on Monte Tumba[1]. Miraculously, when the bishop and companions arrived, a purple cloth was already laid as for an altar, and the archangel's footprint was preserved in the rock.

The Golden Legend (Legenda Aurea), the compendium of Christian mythology compiled by Jacobus de Varagine between 1260-1275, narrates the first of the apparitions of Michael:

“ When he appeared in the Mount of Gargan. This mountain is in Naples, which is named Gargan and is by the city named Syponte. And in the year of our Lord three hundred and ninety, was in the same city of Syponte a man which was named Garganus, which, after some books, had taken that name of the mountain, or else the mountain took the name of the man. And he was right rich, and had a great multitude of sheep and beasts, and as they pastured about the sides of the mountains it happed that a bull left the other beasts, and went upon high on the mountain and returned not home again with the other beasts. Then this rich man, the owner, took a great multitude of servants, and did do seek this bull all about, and at the last he was found on high on the mountain by the entry of a hole or a cave. And then the master was wroth because he had strayed alone from other beasts, and made one of his servants to shoot an arrow at him. And anon the arrow returned with the wind and smote him that had shot it, wherewith they of the city were troubled with this thing, and went to the bishop and inquired of him what was to be done in this thing, that was so wonderful. And then he commanded them to fast three days and to pray unto God. And when this was done Saint Michael appeared to the bishop, saying: Know ye that this man is so hurt by my will. I am Michael the archangel, which will that this place be worshipped in earth, and will have it surely kept. And therefore I have proved that I am keeper of this place by the demonstrance and showing of this thing. And then anon the bishop and they of the city went with procession unto that place, and durst not enter into it, but made their prayers withoutforth. ”

Pope Gelasius I (reigned 492-496) directed that a basilica be erected enclosing the space. The Basilica di San Giovanni in Tumba is the final resting-place of the Lombard king Rothari (d. 652); the designation "tumba" is now applied to the cupola on squinches.[2]

To Michael's dramatic later intercession, appearing with flaming sword atop the mountain, in the midst of a storm on the eve of the battle, the Lombards of Sipontum attributed their victory (May 8, 663) over the Greeks loyal to the Byzantine emperor, and so, in commemoration of this victory, the church of Sipontum instituted a special feast honoring the Archangel, on May 8, which then spread throughout the Catholic Church. Since the time of Pius V it has been formalized as Apparitio S. Michaelis although it originally did not commemorate the apparition, but the victory of the barbarian Lombards over the Orthodox Greeks, faithful subjects of the Byzantine Emperor in the East and the patriarch of Constantinople, and thorns in the papal side.

Christened "Monte Sant' Angelo", the site attracted pilgrims from near and far. Throughout its history the shrine at Monte Gargano has been visited by popes emperors and saints: Bernard of Clairvaux, Thomas Aquinas, Birgitta of Sweden— but when Francis of Assisi went, he declined to enter the grotto itself.

Architecture

The complex of buildings consists of the Battistero di San Giovanni in Tumba, damaged in 1942, and the Church of Santa Maria Maggiore. The baptistery presents a rectangular storey on which rests an octagon supporting an elliptical section and a high drum that supports the cupola. The church erected in the eleventh century by Archbishop Leone stands upon the remains of an ancient necropolis. A few remnants attest to its once-rich fresco decoration.

The Castello was enlarged by the Normans upon an episcopal residence of Orso, Bishop of Benevento, to provide a suitable seat for the Honor Montis Sancti Angeli, further modified by Frederick II.[3] The massive, octagonal campanile was built in the late 13th century by Emperor Frederick II of Sicily as a watchtower. It was turned into a bell tower by Charles I of Anjou.

Behind a forecourt the sanctuary presents a portico of two Gothic arches, the right one of 1395 by the local architect Simone, the left one a reconstruction of 1865. From the portico steps lead down to the low arched nave. The cavern can be accessed from a Romanesque portal, called the Portale del Toro ("Gate of the Bull"): the doors, in bronze, were made in Constantinople in 1076, the donation of an Amalfitan noble. They are divided in 24 panels portraying episodes of angels from the Old and New Testaments.

The archaic cavern opening to the left, with its holy well, is full of votive offerings, especially the 12th century marble bishop's throne supported on crouching lions.[4] Among the ex voto objects is a statue of the Archangel by Andrea Sansovino.