Aniston admitted it was surreal to see the set, which had "the exact same everything, down to the little tchotchkes on the shelves", and contrast their memories of the time they first gathered there until now.
She said: "You know, [in] 16 years, a lot has gone on for each of us.
"And 16 years ago, we were all sort of wide-eyed and bushy-tailed, and sort of had our whole lives ahead of us - even though we were heartbroken to say goodbye to these 10 years and this family and these people and the job we all loved to do.
"It's nostalgic in a way that's kind of also a little melancholy, 'cause a lot has changed, and we have all gone down different roads. Some easy and some not so easy for each of us."
After admitting the reunion was "brutal", the "Cake" actress also acknowledged she couldn't stop crying throughout filming, but she wasn't the only one.
She said: "There was a period where we were all kind of in a puddle. Maybe David didn't, I don't think we broke David."
And she was most surprised to see Matt LeBlanc, who she dubbed "Mr.Tough Guy", in tears.
She said: "Mr Impenetrable, our big brother, who would kill anybody if they looked at you wrong. Even he got a little misty."
