In October of last year the rebel Syrian Democratic Forces with support of the US led coalition entered Raqqa, the former capital of the Islamic State armed group.
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Civilians returning home not only found their property marked and vandalised but also underground tunnels.
The vast underground complex was not only built to provide cover from coalition aerial bombardment; it housed bunkers, storage facilities and escape routes for Islamic State fighters.
In this fourth part in a series of 5, Filip Warwick reports from Raqqa.
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