Why is this code considered O(N^6) in Big Oh notation?

I was just reading another question and this code intrigued me:

for(i = 0; i < n; i++)
{
    for(j = 0; j < i*i; j++)
    {
        for(k = 0; k < i*j; k++)
        {
            pseudo_inner_count++;
            for(l = 0; l < 10; l++);
        }
    }
}

I don't understand how this can be O(N^6). Can someone break it down for me?