In much of Children’s fiction, the Child is transported to a fantastic land by means of a gateway of some kind. C.S. Lewis’s “The Lion, The Witch, and The Wardrobe” possesses one of the most literal and iconic of these gateways: the wardrobe.
The rest of the series also possesses such portals or gateways: a magic ring in “The Magician’s Nephew,” and a portrait in “The Voyage of the Dawn Treader.” C.S. Lewis was not the first to use this mechanism, though.
In L. Frank Baum’s “The Wizard of Oz,” the twister transports Dorothy from Kansas to Munchkinland.
Peter Pan and Wendy fly to the second star to the right. Alice gets to Wonderland through means of the rabbit hole, and even in “The Water Babies,” Tom is transported when he falls in the river.
In modern times, the gateway has become a ubiquitous means of transporting the protagonist into a fantastic world, and has even departed the realm of Children’s Literature. A machine turns a paraplegic into a nine foot tall blue man with a hair tail. A girl travels through a tree in the middle of a labyrinth in Spain. An entire team travels through an alien portal to various other worlds. A man is transported by a church bell to 1920’s Paris. Neo takes the red pill.
Why has the portal to another world become so ubiquitous? Perhaps it is because it is a simple way to show a distinct change between the real world and the fantastic one. But perhaps it is because the portal allows for the suspension of disbelief–once you go through the portal, anything can happen.