When you think of Dishonored, what's the first image that comes to mind? Rats, blades, haunted hearts and clockwork mansions? Perhaps it's cramped streets, a bleeding whale, or an arterial river. For many of us, it's a city. We asked Rob Dwiar, a garden designer, landscape architect, horticulturist and writer, to look at a specific aspect of those cities. The gardens. There's a whole lot…