Build a spiral staircase to the sky in Unity3d.

StairCaseBuilder.cs

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

/*
Attach this script to an empty object positioned at where you want to have the bottom center of the staircase.
Drag a prefab of a step of the staircase to the "Step Prefab" field.
The prefab of a step could simply be a cube with position scale to (2.5, 0.2, 2.5). 
*/

public class BuildStairCase : MonoBehaviour {
	public GameObject stepPrefab;
	// Use this for initialization
	void Start () {
		Vector3 centerBottom = gameObject.transform.position;
		float radius = 5f;
		float angleDegrees = 10f;
		float angleRadians = angleDegrees * Mathf.PI / 180f;
		for (var i = 0; i < 100; i++) {
			float x = radius * Mathf.Cos (i * angleRadians);
			float z = radius * Mathf.Sin (i * angleRadians);
			Vector3 pos = new Vector3(centerBottom.x + x, centerBottom.y + i * .2f, centerBottom.z + z);
			Quaternion rot = new Quaternion ();
			GameObject step = Instantiate(stepPrefab, pos, rot);
			step.transform.Rotate (0, -i * angleDegrees, 0);
		}
	}
}