Exploring a hidden underground city in Turkey
At the heart of Nevsehir in Turkey lies an underground city which could extend over 450,000 square meters (4,800,000 square feet).
It was discovered when a hillside was being cleared for redevelopment.
A monastery dating back to the 6th Century, burial chambers and an underground church have been uncovered by the ongoing excavations.
The Nevsehir region is known for underground cities and villages - more than 200 cities and villages exist - and is recognised as an Unesco World Heritage Site.
The BBC Travel Show's Henry Golding went to find out more.
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