Michaelangelo designed these flowing stairs in a very small entry vestibule leading to the Laurentian Library reading room. (next picture).
The stairs have been likened to "a descending tumble of waves" due to their appearance of "flowing" down from the upper area built over a monastic wing of San Lorenzo.
Michelangelo designed what could have been an ordinary staircase but instead is magnificent sculptural entity.

The staircase was actually constructed by Ammannati in 1559, following a clay model prepared by Michelangelo.
It consists of three sets of steps...the outer ones which are rectangular in shape, leading to the reading room,
and the central steps in a descending scallop shape.
The bottom three steps of the central area are softened with a broader curved form.
The staircase is then, is a good example of Mannerist archiecture, using a variety of opposing forms combined.