Without it, the site first opened to the public in 2015. It featured about 120,000 square feet of new or reconfigured exhibition space; a new cinema; a new two-story Miesian pavilion of wide open gallery spaces, called the Podium, the whole building clad in light, shimmery panels of foamed aluminum, an automotive and medical industry material also used for bomb blast absorption that looks a little like rough stone. There was even a 1950s-style Italian cafe straight out of a Wes Anderson movie.

That was because Wes Anderson designed it.

Chameleons themselves, Mr. Koolhaas and Ms. Prada made natural confederates. She was the famous communist turned high-fashion mogul whose empire evolved from bags and backpacks constructed out of an industrial nylon lining material. He was a prophet of global cities who declared the countryside his real passion after everyone else jumped on the urbanist bandwagon.

Her clothes always seemed less about what men desired than what whet her creative appetite. He was once invited to propose an expansion for the Museum of Modern Art and thumbed his nose at the selection committee by suggesting a billboard that said “MoMA Inc.” They were both contrarians and closet optimists.

And they shared a sense of humor. At one time it was rumored that Prada might back the Dutch architect for a seat in the Italian Parliament.