It’s been in the works for a decade, but with the opening of the Brooklyn Academy of Music’s new Fisher Building, it finally looks like a reality: The blooming of a high-density arts enclave in an outer-borough neighborhood that once seemed to Manhattan culture vultures like a risky trip across the river.

Look right up the street from the Fisher — an intimate, ultra-flexible space that this fall brings legit work by Samuel Beckett and docu-theater troupe the Civilians to Brooklyn as part of its multidisciplinary programming — and you’ll spot the rising outpost of Theater for a New Audience, targeting a fall 2013 launch with a new Shakespeare production from Julie Taymor.

BAM, founded in 1861 and evolving over the past 40 years into a prestigious presenter of often-arty international fare, is the anchor for the cultural growth in Fort Greene, Brooklyn, where the nonprofit’s three venues are joined by the home bases of Mark Morris Dance Group, music venue Roulette and legit new-work developer Page 73 Prods., among several other orgs. Hefty support from city government has also helped prompt growth in the so-called BAM Cultural District, and was one of the things that attracted Theater for a New Audience to the area.

For BAM, the Fisher adds a small-scale space — which seats a max of 250, depending on the configuration — to provide the programming flexibility that BAM’s 2,100-seat opera house and its 870-seat second stage can’t accommodate.BAM execs especially tout the ceiling’s tension wire grid that allows for any arrangement of tech elements.

This fall, solo performers Marc Bamuthi Joseph and Derrick Adams join the Civilians’ “Paris Commune” and Beckett’s “All That Fall” by Ireland’s Pan Pan Theater Company on the Fisher’s legit lineup for BAM’s annual Next Wave Festival, with all Fisher offerings topping out at $20 per ticket.

The $50 million, seven-story, 40,000-square-foot building — which includes rehearsal studio, staff offices and classrooms — will be freed up in the spring to expand BAM’s family programming and other activities, as well as allowing for rental space to community arts orgs.

“Before the Fisher, we were prevented from being responsive to the artistic needs of the burgeoning Brooklyn creative community,” says Melillo.

The prospect of engaging the local community also is a draw for Theater for a New Audience, the 33-year-old legit nonprofit that’s never had a performance space to call its own. “Two things you want are diversity and density, and this area has them,” says TFANA founder Jeffrey Horowitz.

At this point, the $52.5 million building, centered on a 299-seat main stage designed for classic drama, looks right at home in Fort Greene. But Horowitz notes that back in 2000, when the theater’s leadership initially decided to pursue building a home on the other side of the East River, Brooklyn seemed a long way from being the coolest city in the world, as GQ magazine dubbed the burg last year.

“Many of our board members were highly skeptical back then,” Horowitz remembers. “Now, of course, they’re tickled pink.”