Gateways, portals, wormholes, star gates, and other such passageways leading to fantasy worlds usher a reader's imagination into realms beyond our imagination.
Create a gateway. What does the person entering glean about the world beyond as they make their approach? How is it activated? How does it feel to step up to the threshold? Does your character enter or does something make them change their mind? If they step through what's the first thing they smell?