Stelios Faitakis, for instance — a Greek artist who combines a Byzantine visual idiom with hot political content — had a mural prominently placed at the last Venice Biennale, and now has a flourishing career on the international contemporary art circuit. But at the opening I attended, two short blocks away from Faitakis’s earliest extant mural (now just a weather-beaten fragment), an art critic I spoke to insisted that the “golden age” of street art in Athens had ended 10 years ago. “You are among the ruins!” he concluded with a flourish.

Given our location — a 10-minute walk from the Acropolis — and Greece’s current economic plight, I thought this was wonderfully droll.

Otavio Pandolfo and his brother Gustavo, who call themselves Os Gemeos (Portuguese for “the twins,” which in fact they are), are street artists from Brazil. They have a sprightly, one-room show at the Institute of Contemporary Art, which is complemented by three murals around the Boston area.

The largest covers the exterior wall of a giant air intake structure on the Rose F. Kennedy Greenway. It’s by far the most successful piece of public art I’ve seen in Boston in the more than four years I’ve lived here.

Another is on the façade of the Revere Hotel Boston Common a few streets away, and a third — a collaboration with local artists RIZE, Todd James, and Caleb Neelon — is on the wall of Mama Gina’s restaurant in Union Square, Somerville.

Like Faitakis and America’s Barry McGee and Shepard Fairey, who all started out as street artists, Os Gemeos are now feted in the contemporary art world, requiring that they straddle a sometimes awkward divide: between the prestige (and oftentimes the pretension) of contemporary art and the edginess (and oftentimes the illegality) of street art.

Does such art-world recognition inevitably entail the domestication of all that makes street art dangerous and interesting? Does it signal an end of things, even a whiff of cultural ruin?

It all depends on your perspective. After all, one man’s cultural ruin is another man’s restoration of law and order. But it’s an interesting moment in the evolution of the street art phenomenon from “urban blight” to institutional co-option.

Os Gemeos grew up in Sao Paolo, where they absorbed an ethic of improvisation — a defining characteristic of their work even now — and a love of Brazilian traditional dress and patterning. They discovered American hip-hop culture in the mid 1980s.

“Wild Style,” an influential film about hip-hop, was a big early influence, reports curator Pedro Alonzo in the exhibition catalog. So was the humorous and socially critical work of McGee, one of the first graffiti artists to use figurative imagery in his work. McGee contacted the twins on a trip to Brazil in 1993.

The Os Gemeos show is the latest in a series of shows the ICA has dedicated to popular street artists, including Fairey and the Mexican tattoo artist Dr Lakra. (McGee is to be the subject of an upcoming show.) Fairey, in particular, proved controversial, and so already have Os Gemeos. A local television news segment about their Greenway mural included interviews with members of the public who thought the mural resembled a terrorist or “Bart Simpson in a Mujahideen outfit.”

Nice, but slightly off the mark. It actually shows a boy in patterned pajamas, huddled up against the edges of the giant wall. Yes, he also wears a shirt wrapped around his head, mouth and nose; but many of Os Gemeos’s unwaveringly cute characters wear similar headwear.

The face covering, of course, is obligatory street artist gear, originally adopted both to protect the airways from spray paint fumes and, like the similarly ubiquitous hoodie, to conceal identity (spray painting is, at least in its illegal forms, necessarily a hit-and-run affair). Now it’s a symbol: a sign of tribal belonging as much as an emblem of urban defiance.