Nearly everywhere I've been, popular wisdom has it that the location of humanity's original planet is unknown, mysterious. In fact it isn't, as anyone who troubles to read on the subject will discover, but it very, very, far away from nearly anywhere, and not a tremendously interesting place. Or at the very least, not nearly as interesting as the enchanting idea that your people are not newcomers to their homes but in fact only recolonized the place they had belonged from the beginning of time. One meets this claim anywhere one finds a remotely human-habitable planet.