Wilfried Eckstein, a member of the European Union National Institutes for Culture, said his group generally focuses on Washington, D.C., but was intrigued by Baltimore's arts scene. Many of the European nations are also dealing with the post-industrial challenges that Baltimore faces, he said.

In addition to the mural project, the European cultural group is helping to fund a series of art works at Baltimore transit hubs. They'll be sponsoring three parkour performers at Penn Station later this month in conjunction with Open Walls.

Nanook said that the out-of-town muralists would stay in apartments in Station North while they were working on their walls. Members of Baltimore Heritage would give them tours of the neighborhood, and they would be encouraged to wander around, meeting residents and business owners.

It's important for artists to channel the energy of the people who live and work near the mural into their work, Nanook said. When he created a mural at Barclay and Lanvale streets for the first Open Walls program, he spent days researching the neighborhood's history and chatting with residents.

"It got me out of my outsider's point of view," said Nanook, a 2011 MICA grad. "I wanted to create something applicable to their lives."

But some question whether the Open Walls muralists seek enough participation from the community.

As Gaia laid out the design on the wall on a Sunday evening, members of the activist group the People's Power Assembly, which meets across the street, questioned why there had not been more advance notice of the project. Gaia said that he and the Station North group had reached out to community leaders, but — although he wished he could — it would be impossible to speak with everyone who would live with the wall.

Others in the neighborhood had little interest in the mural. The clerk at the Halal grocery store up the block hadn't seen it. Juan Perez, an employee of Papi's convenience store a block away, wondered why a beautification project would be prioritized in a city with so many other challenges.

But many of the people who passed by the mural were intrigued by the images Gaia brought forth. They paused and gazed for a long time, called out in admiration or stepped up to chat with the artist, who was bundled against the unusually chilly spring days in a hunter's camouflage jacket.

"I'm an artist, too. Let me show you my work," said Chae Harris, 17, a senior at Cristo Rey High School, who was heading home from school. He pulled the beginnings of a pencil sketch of a woman's face from a folder.

"Hell yeah," said Gaia, nodding. "Let me know if you want to get involved with helping any of the artists out."

Gaia got his start by hanging out with established street artists when he was growing up on the Upper East Side of New York. His work had already gained a following by the time he moved to Baltimore eight years ago to attend MICA.

His distinctive pieces from that time period — evocative figures blending human and animal characteristics — popped up on buildings around Station North, affixed to walls with wheat paste. Since then, he has been commissioned to create works around the world. He has had a solo show at the Baltimore Museum of Art and been featured in The New York Times and The Washington Post.

He spends about three months of the year in Baltimore, hanging out with arabbers, painting murals on car repair shops, creating art for free. These days, he primarily works in paint, forgoing the wheat paste images that were his earlier trademark.

The mural, which he called "Horizons," speaks to the neighborhood's diversity and state of flux.

"This piece is about the changing nature of this community," he said. "There are so many directions it could go. And there's fear invested in that."

Michelle Owens stopped her motorized scooter on a recent afternoon to chat with Gaia. Her little puff of a dog, Jazz, was balanced on her lap. It was her 69th birthday and Owens was heading back to her apartment on the 16th floor of the high rise to listen to music. She takes Jazz to the lot a few times a day and thinks the mural adds much to the view.

"It's nice to look at," she said. "It makes you think."

Robert Grant, 62, studied the mural for a long time as he passed by on his way home from the garage where he does odd jobs.

"You get a feeling from it," he said. "The sky above the mountains tells you you're in this world, but the head" — the bust of Mercury — "tells you you're not."

Gaia decided to leave some parts of the mural apparently unfinished. The tiger's face is rendered in fine detail, but its body trails off in an outline. The body of the man in the foreground, a third-generation arabber named James Chase, fades into a blur of brush strokes. The old sign for "Seoul Rice Cakes" shines through his shirt.

"I never try to completely finish the piece," he said. "It's a thesis without a conclusion, rather than a full statement."

Sitting on a log opposite the mural, Aileen Brown recounted a series of misfortunes. She's been ill and recently became homeless, she said.

"It's a shot of hope," she said of the mural. "Despite everything that's happened, this represents that there's hope."