Here's one of my favorite funny art piece located near my place when I was in London. First I saw it, I thought there must have loads of accidents happen for sure. But I saw none!!! all the drivers seem to be able to manage it perfectly :-P
Strategies for subversive urban occupation Public Domain Occupation with skips Sevilla, 1997
House enlarging with scaffolding Sevilla, 1998
Tree occupation with insect house Sevilla, 2001
from his website: Reasons for building one-self an urban reserve can be as many as citizens are, that dare doing it. What man can certainly say, is that this personal and intimate action takes place outside everything politicians and professionals may plan, it follows ways that are labelled by difference, by independence, and it makes obvious that the citizen plays a very important role in the development and construction of the environment he lives in.