This is interpreted as the premonition of the Four Evangelists.In the 12th century, Venice was on the fast track to becoming the dominant sea-faring republic in Europe. She was getting wealthy from spoils and trade. It was about this time that she decided she needed a glamorous, ‘Hollywood’ beginning, one that would become legendary throughout the lands and elevate her above all other nations.
Venice began to spread the legend that, while Mark was passing through the Venetian lagoon in the 1st century AD, an angel appeared to him while he was napping and announced that the location where the future Saint Mark’s Basilica would be built was to be his final resting spot, and that he would be protected by these great people. The angel began his encounter with Mark by saying “Peace unto you, Mark, my Evangelist.”
Mark was killed in Alexandria in 68 AD and a huge storm immediately after his death (a miraculous intervention?) made it possible for Christians to take his body from his persecutors and give him a Christian burial, and he was kept in a local monastery. In the 9th century the area was under Moorish domination and no longer secure, so two Venetian merchants took the matter into their own hands and smuggled Mark’s body out of Alexandria to Venice, where he would receive eternal protection and worthy veneration.