Do you see beauty in a cinder block wall, a street crossing or a stop sign? Chances are, you don’t even notice them – but Aakash Nihalani would like to help you out with that. The Brooklyn-based street artist calls attention to the mundane using bright rolls of tape, bringing out extra dimensions that incite passersby to take a second look at their surroundings.

Currently finishing up an interactive design festival in France, the Les Grandes Traversees, Nihalani has gained wide renown for his 3D urban art. The artist freehands his typically geometric tape designs, sometimes directly on a surface (as quickly as possible) and sometimes on a cardboard backing to produce a rigid cutout that can stand alone.

Asked whether he ever tussles with authorities over removing his work, Nihalani said, “I’ve asked cops and maintenance staff to wait for me to take a quick photo before they start taking it down, and most have let me.”

“There’s also been plenty of instances of workers walking past me and not saying anything even though they see me taping. And on very rare occasions a person in uniform will stop just to share some positive feedback, human to human.”

People tend to think of graffiti as being necessarily illegal. While that may be the case much of the time, not all guerilla art breaks the law. Many urban artists manage to be creatively but legally subversive. Here are some engaging types and works of visual and performance art that have prompted critical thought or stirred up controversy, all without getting the artist(s) in trouble.

(Check out our complete collection of 100+ Works of Creative and Geeky Art and Graffiti.)

Reverse Graffiti is a classic example of urban art that confounds authorities. In most cases, the police are helpless, unable to fine or arrest someone for cleaning public surfaces. Shown above is the wall work of Symbolix, also known for creative guerilla marketing, as well as the dirty car art of Scott Wade.

Flash Mobs form and dissipate as a type of spontaneous-but-organized urban performance art. Groups of friends (or strangers) coordinate their efforts online and gather at a pre-defined time in a public space – seemingly out of nowhere. Flash mobs can be planned to do almost anything, from hijacking a furniture store to throwing a train-station dance party.

City Statues may seem like the last form of art that could possibly be subversive. However, these statues are far from the ordinary tributes to statesmen or national heroes. Each of these is designed to be interactive, satirical or engaging beyond merely historical references.

Other Kinds of guerilla communication from glowstick graffiti to guerilla marketing are also legal – as they either leave no trace or even get official approval. The work of infamous street artist Banksy is so popular that, despite being technically illegal, people have been arrested for defacing his graffiti. Be sure to check out these other amazing works of urban guerilla street art.

Next: More Unusually Legal Street Art