“I always like to put things that are a little bit ironic together. So here you have a place like BAM, which is a great contemporary-arts cultural institution, and then you have an arena, which, people think about sports and circus and so on. And then you put them together, and then I think you’ve got something special.”

Indeed, Mr. Ratner has been a master of irony through decades of development:

• He had a rapidly gentrifying stretch of Brooklyn declared blighted, and then condemned.
• He has acquired a taste for hip-hop.
• He gets the light touch from the newspaper of record whose headquarters he built.
• He lives in Manhattan.
• He hired, then fired, Frank Gehry from the Atlantic Yards project after a lifetime of developing blasé buildings.
• Ratner's rats.

(If these are not exactly ironic, well, neither is a cultural institution putting on shows in a sports arena, either.)