Artwork that is in the public realm, regardless of whether it is situated on public or private property or whether it has been purchased with public or private money. Usually, but not always, the art has been commissioned specifically for the site in which it is situated. Monuments, memorials and civic statues and sculptures are the most established forms of public art, but public art can also be transitory, in the form of performances, dance, theatre, poetry, graffiti, posters and installations. Public art can often be used as a political tool, like the propaganda posters and statues of the Soviet Union or the murals painted by the Ulster Unionists in Northern Ireland. Public art can also be a form of civic protest, as in the graffiti sprayed on the side of the New York subway in the 1980s.