I'm almost positive the only reality other than this one that may be thoroughly investigated is the dream reality. And even the dream reality comes only from our minds, such as spiritual or religious ideas. They can be explored only as much as your imagination can take you, but remember, imagination is not truth... it is speculation of ideas without any basis for physical examination. Therefor these ideas always have some doubt behind them, as they cannot stand up to the burdens of proof required to perceive these ideas as real.
(Which is exactly why "faith" is a requirement when attempting to claim truth to an idea (yes, beliefs are IDEAS) without any truth value)
Whomever perceives these fantasy ideas as real is faced with an inner conflict, or contradiction. As the true self knows that these ideas have no basis in reality, nor have they been proved beyond reasonable doubt except in the mind of the individual. The individual does everything possible to keep from consciously acknowledging he/she is not certain of their "beliefs" as to not be faced with this inner conflict, or contradiction.
Though it is fun to think about these fantastical ideas and concepts, they must be left at the door of fantasy for us to keep touch with what is real in the only reality we can measure accurately, this one.
"Uncertainty in the presence of vivid hopes, dreams and fears is very painful... but must be endured if we wish to live our lives without the support of comforting fairy tales." -Bertrand Russell
Edit:
The greatest thing about science is that no one is required to believe anything! Regardless of what you do or do not believe, gravity exists. Take an object and hold it above your head, drop it, gravity. No need to believe.
With religion/spirituality, you are required to believe in order for it to be true or real... with science you do not. Point made.