This staircase is inspired by the spiral staircase in the new set Pet Shop 10128 
In the new set it is a spiral staircase based on a 1 x 4 plate.
(see e.g. pics on http://www.eurobricks.com/bonaparte/images/petshop/pet-10.jpg)

I experimented with different size plates
and came up with this staircase based on a 2 x 6 plate.

I decorated it with a colourfull carpet 
and made convenient banisters.

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