I have searched for the specific barbie movie I had in mind and I can’t seem to find it. I just remember that barbie was like exploring some castle like thing because she was sent there alone. She walked around and then in one big room, the floor opened up and had a circular magical hole in it, which led to a different world where the grass was minty green and I love that sort of stuff
Looks like the movie you’re referring to is ‘Barbie and the Secret Door’ (2004). If not, it might be in this list https://www.polygon.com/23803316/barbie-movies-ranked-animation-where-to-stream