The Islamic State -- or ISIS -- stormed into Iraq's second largest city, Mosul, last summer and took control. From there, it pushed into the neighboring villages and towns across this region, known as the Nineveh Plains, a vast area that's been home to Christians since the first century after Christ. Much of what took almost 2,000 years to build has been lost in a matter of months.
On the side of a mountain, overlooking the Nineveh Plains of ancient Mesopotamia, is the Monastery of St. Matthew. It's one of the oldest on earth.
The voices of its monks have echoed here since the fourth century, uttering prayers that have not changed.