A few years ago I read this book about how Alexander the Great's body got misidentified as St Mark's when it was smuggled out of Alexandria by two well-meaning Copts during the 7th c Islamic conquests, and is still in Vienna today. 1/

Later I visited Vienna (unrelated trip) and checked out a small museum of artifacts from Mark's crypt dated to the cathedral's founding.

This relief of a Macedonian shield and sarissa (dated to 4th c BCE by an Hellenic expert) was found in the tomb adjacent to the sarcophagus.

Basically the idea is that the shrine of Alexander's tomb fell into disrepair and was eventually forgotten in Coptic Christian Alexandria.

A 4th c Bishop referrered to Alexander's grave as lost in a sermon illustration, to emphasize how all human glory fades.

Around the 4th century, however, Mark's tomb (Mark is thought to have been martyred in Alexandria) became a source of serious Coptic pride, and a major pilgrimage destination.

Mark's body is said to have been embalmed - just like Alexander's.

The story goes that, soon after Alexander's city fell to 'Amr's conquering seige forces, two Copts took Mark's body from the shrine and hid it in a merchant vessel's shipment of pork. Muslim inspectors left the haram shipment alone, and the copts sailed to Byzantine Venice.

And St Mark's tomb has been the centerpoint of Venice's Bascillica ever since.

The guy who put this theory together has asked the Venetian bishopric and the Italian govt to evaluate St Mark's body - to no avail, of course.

Anyway that's the story as I've heard it.