Baghdad, Iraq (CNN) Two floors beneath the headquarters of Iraqi Military Intelligence, at the end of a red-carpeted corridor, two doors swing open to reveal a museum of cold, calculated and deliberate horror.

This is no celebration of the darkest chapter in Iraq's recent bloody history -- rather it is a warning of how dangerously efficient were those who dreamed of establishing a "caliphate" in Iraq and Syria.

It's a stomach-heaving experience to recall how they wiped the history in a swath of this nation by destroying any trace of non-Islamic culture in the areas they controlled, blowing up ancient buildings and archeological sites dating back millennia.

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The staggering brutality of ISIS, what the terrorists called the "management of savagery," was meticulously recorded and posted on the internet to morbidly fascinate the world and ensure absolute obedience in the regions under its control.

ISIS's reach was massive -- they covered a territory the size of the United Kingdom with up to 12 million people in it -- but it's the small things in the museum, the Nazi-like obsession with records, files, and documentation, that send the visitor reeling.

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