Again, if you contemplate an extra dimension, that does not mean that fifth dimension is another 3D realm hidden behind some portal. It means that our world is 5-dimensional. You can see what it means when you compare 3D cube and its 4D analogue, tesseract (or one 2D square that is an inseparable side of a 3D cube).

https://en.wikipedia.org/wiki/Tesseract