Strictly speaking, it might not be a dream. It was reality, but a reality imbued with all the qualities of a dream. A different sphere of reality, where - at a special time and place - imagination had been set free.

They say it's a dangerous experiment to include dreams (actual dreams or otherwise) in the fiction you write. Only a handful of writers - and I'm talking the most talented - are able to pull off the irrational synthesis you find in dreams.