It got its name because, supposedly, condemned prisoners passed over this bridge to their fate, catching a last glimpse of the free world through the pierced windows. And sighed in regret.
This is the Grand Canal, Venice's "main drag."
The larger light yellow boat on the center left side of the picture is public transportation--a "vaporetto." Most of the locals use these, as water taxis are quite expensive. And gondolas are slow and basically for tourists.