There are many types of stairs according to the rules of civil engineering: straight stairs, dogged-legged stairs, open newel stair, geometrical stair, circular stair, spiral stair, quarter-turn stair, bifurcated stair. All these should be build in special circumstances, when the building interior (or exterior) is asking for certain type.  The way they all look like is showed bellow in the images and more precise are all given in the link bellow. Check them out!

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