In a forty year career in architecture, I've used gargoyles only a handful of times. They're not really suitable for urban architecture because in high density areas spewing rain onto the hardscape can be a public nuisance. read more
Architects often used multiple gargoyles on a building to divide the flow of rainwater off the roof to minimize the potential damage from a rainstorm. A trough is cut in the back of the gargoyle and rainwater typically exits through the open mouth. read more