Probably CGI
This is, in fact, a re-designed Avengers Tower that Tony Stark sold in Spider-Man: Homecoming.
Since the old Avengers Tower was CGI, it's likely that this new building is also CGI.
At the end of Spider-Man: Far From Home, Spider-Man swings past (and through) the redesigned building, giving audiences a glimpse at what it has now become. The most notable change that is visible is a gaping hole in the center. This is by design and not a result of another giant fight in New York. The gap is used as a lounge and garden area for the building, which has a modern, hi-tech feel to it. Beyond this, it isn't clear what the functionality of the hole is, other than giving Spider-Man the ability to swing through the building instead of around it.
The new look makes the towering structure stand out even more than it did before, but Spider-Man: Far From Home stops short of showing us who is in the building or what name/company is branded on it.
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