Heraclius (c.575–641) was Eastern Roman emperor from 610 to 641. The lagoon city of Eraclea was named after him.
This document is the earliest description of the translation of St Mark to Venice in 827–828, and also of early Venice. This is a translation by René Seindal.
The Birthday of Venice of is traditionally on March 25th, 421 CE, but this is far more legend than historical truth.