Wonderland was the titular setting of Lewis Carroll's Alice in Wonderland.
According to some accounts, Lewis's book was based on real events, with Alice Liddell having been Lewis Carroll's neighbour in Oxford; (PROSE: The Wildthyme Effect) Wonderland truly existed beneath the Earth's crust. Its inhabitants referred to the outside world as "the rational world". Its existence was made tangible by Harriet Dodd using a feasibility generator, a device which could make the existence of impossible things "more probable", and she used it as an "underground zoo of freaks" for the various interdimensional beings and other "irrational" creatures that MIAOW would capture. (AUDIO: Iris Wildthyme and the Land of Wonder)
When the fictional Alice Liddell succeeded Zoe Heriot as Mistress of the Land, the Land of Fiction began to evolve into a very different place, a "Wonderland", with Alice as its "Queen of Hearts". (AUDIO: Legend of the Cybermen)