Container isn't pivoting around the center of itself, why?

Below is the code I am using. If you load this into unity you’ll notice that instead of rotating around the center of the cube made of cubes that it is rotating around another point.

I tried the solution from this question, but it just doesn’t seem to be working:
How do I rotate and object around its center in script?

Can anyone shed light on what I am doing wrong? Thanks in advance.

using UnityEngine;
using System.Collections;

public class BlockContainer : MonoBehaviour {
	private GameObject _container;
	private ArrayList _containerPointers;
	// Use this for initialization
	void Start () {
		GameObject cube;
		Color red;
		_containerPointers = new ArrayList();
		_container = new GameObject("BlockContainer");
		red = new Color(1.0f, 0.0f, 0.0f);
		for(int i = 0; i < 2; i++){
			for(int j = 0; j < 2; j++){
				for(int k = 0; k < 2; k++){
					cube = GameObject.CreatePrimitive(PrimitiveType.Cube);
					cube.renderer.material.color = red;
					cube.transform.parent = _container.transform;

	// Update is called once per frame
	void Update () {
		_container.transform.RotateAround(, Vector3.up, 1.0f);

All of the cubes that compose the container are on the positive side of the local origin. Try Looping from -1 to 1 instead of from 0 to 2.