the phallus of righteous justice

It seems so obvious in hindsight, but if you're thinking of defacing large areas of land with crude portrayals of giant spurting cocks - and who hasn't at least considered that at one time or another? - then actually snow is pretty much the perfect medium. Yes, you can go around with a can of weedkiller, possibly concealed up a trouser leg Great Escape stylee, and kill some grass, or hang precariously off a roof while daubing it with paint, but it's a lot of effort, and there'll probably be some sort of community service court order served on you whereby you have to go and clear it up afterwards, unless you can persuade your local council to do it for you.

Snow, on the other hand, is easy to manipulate, and - unless you live in Antarctica - there's a transient, ephemeral nature to it so that it'll eventually fade away without any intervention being required. The extra element of cleverness with this one in Gothenburg, Sweden is that it was drawn (at some degree of personal risk to the perpetrator, one assumes) on a frozen lake in a park, so that it was a while before the dead corporate hand of The Man was able to come up with a Health & Safety-compliant way of removing it. 

The rather glorious footnote is that one of the officials tasked with removing the original, relatively small snow cock was so racked with guilt at what he had done that he organised the construction of a much larger, many times more magnificent cock in a nearby park.

As stupendous as this is, the guy who constructed it has made a bit of a schoolboy error: a crudely-daubed cock is not complete unless it has all spunk coming out of the end. Honestly, it's like these people know nothing.

If even snow-based cock-daubing seems a bit high-risk for you, then how about this: going out for a walk or a jog or a run with your GPS device and trying to make your route conform as closely as possible to the shape of a cock. It almost goes without saying that there is a whole website devoted to people drawing GPS cocks. If you have access to an aeroplane you can do much the same thing on a somewhat larger scale.