From time to time, you will see bas-reliefs that look like this around Venice. I wondered who this represented, and now I know who it is, it’s Santa Barbara.
She is the patron saint of artillerymen, military engineers, miners and others who work with explosives, her feast day is 4 December.
The tower in her left hand represents the one in which her father detained her, to keep her from the evils of the external world. She had secretly become a Christian, and when she was condemned to death by beheading, one legend relates that her father carried out this sentence. He got his comeuppance when he was struck by lightning, and consumed in flames.
That is a palm branch in her right hand; sometimes she is shown with cannons or cannon barrels.
So, when you see a depiction that looks something like this, you’ll recognise this martyr.
PS You may also spot this pretty lady, whose name is also Barbara, but I can’t verify that she is a saint!