City of Naours
- Episode aired Oct 30, 2019
- 44m
![Underground Marvels (2019)](https://m.media-amazon.com/images/M/MV5BMTg2MGYwMDktMmNmOC00Zjk3LWFjMGUtZWNmMWQ3Njk4OTRlXkEyXkFqcGdeQXVyNDQ0NjMyOA@@._V1_QL75_UY281_CR155,0,190,281_.jpg)
An underground city beneath a forest in Northern France built to house 3,000 people, an ice cave under Iceland's biggest glacier, and a subterranean power station in London.An underground city beneath a forest in Northern France built to house 3,000 people, an ice cave under Iceland's biggest glacier, and a subterranean power station in London.An underground city beneath a forest in Northern France built to house 3,000 people, an ice cave under Iceland's biggest glacier, and a subterranean power station in London.