I built it as a workshop where I make things I need and do repairs on things that have broken or stopped working.
I have always wanted to build a TARDIS but never had a good enough excuse. When I decided to dismantle my existing shed and rebuilt it to my exact needs It occurred to me that the concept of the TARDIS was very much what I wanted in a shed. It should look as small as a telephone box on the outside but actually be as big as the Universe inside.