Spiral climb in surrounding enclosure

A modular spiral staircase contained within a surrounding enclosure, comprising:

• a plurality of arcuate tread segments radiating outwardly from a supporting central post;
• the supporting central post being a height generally corresponding to the height of the plurality of accurate tread segments to provide inner lateral and vertical support for the plurality of accurate tread segments;
• the supporting central posts of adjacent individual stair treads being vertically connected to one another;
• the plurality of arcuate tread segments defining individual stair treads each having an upper planar wall, side walls and a curvilinear depending outer end wall;
• a sidewall of a lower tread segment in an upper plurality of arcuate tread segments being connected to a sidewall of an upper tread segment in a lower plurality of arcuate tread segments at a position spaced form the corresponding supporting central posts;
• and
• the curvilinear depending outer end wall of each arcuate tread segment being circumferentially engaged by and connected to a surrounding enclosure.