Venice's claim to St Mark was tenuous at best; there is no historical or biblical evidence that the Evangelist was ever anywhere near the city. Records in the 6th century state that St Fortunatus was the greatest saint of Aquileia, just as Mark was the greatest saint of Egypt.
That, however, never stopped the resourceful Republic from coming up with a useful self-justifying legend for the 'translation' of Mark's relics from Alexandria, making up a story in the 10th century that Saint Mark had been driven ashore by a storm on his way from Aquileia to Alexandria.
The 'exact spot' is marked by the church of San Francesco della Vigna, where an angel appeared and informed him that the Lagoon would someday be his resting place:
Pax tibi Marce, evangelista meus. Hic requiescet corpus tuum
(Peace be with you Mark, my evangelist. Here your body will rest)
The angel added that 'the city that shall rise on these lagoons will call you its protector'. St Mark would prove it on several occasions, notably when he joined forces with St George and St Nicholas to save Venice from a boatload of devils.
Images by original photo Shakko, PD Art