There are indeed doors to rooms and spaces in higher dimensions. In the small world of the atoms there are less dimensions as in our world in which we live. Therefore we have gigantic forces in the atomic world which we can see unfolded in atomic reactions. And on the other hand we have the "weaker" gravitational forces in the universe which is the result of more dimensions in bigger spaces. Therefore there are doors into other worlds but only as big as planets. They are called Black Holes and travelling with a planet through a Black Hole we could really ship into new worlds and maybe going back to the times of the Roman or Egyptian Empire. So yes the whole planet can do this but not the little people for their own. They are too small to do that.