Haram refers to the sacredness, every religion finds the sacredness and signs of God in certain things, like the Sun, the human reproductive organs, the cow, the stars, hills , the angels etc.. In Islam the masjid itself is Haram(sacredness) as there is nothing to be associated with, so the belief/thought, there is nothing that can be associated with HIM is the masjid Al Haram and it becomes the focus, ie Purity of mind and body is the focus. It starts from the story of Abraham and the state of his mind that all encompassing is his creations and signs. but Quran also asks us to respects the signs an also respects the prophets, the angels etc.
