Venice in Theodomirus' years
In the years of the Cohors Arcana, Venice was not a lagoon yet. When Latin authors wrote about Venetia, they were referring to the area between the rivers Sile and Medoacus (Brenta). This area is full of ponds and waterways branching towards the Adriatic sea; however where today there are canals, there once was solid terrain. The most important town here was Metamauco (near modern day Malamocco), a commercial harbor under Padua's control, located at the mouth of the river Brenta.
In Theodomirus' times, this region was fortified and several canals were dug between the rivers, to make the whole basin more functional.
This does not mean, however, that an adventure in the upper Adriatic area would lack charm and mystery. Expeditions to fight the Illyrian pirates of the Quarnaro Gulf or to look for the lost Adriatis, the submerged city, could start from Metamauco.