Underground tunnel, 地下隧道

Danilovskiy brook, Moscow. (Anna Arinova/ Caters News)

Motolskiy brook in Prague. (Anna Arinova/ Caters News)

ZIL plant in Moscow. (Anna Arinova/ Caters News)
Underground tunnels
https://www.yahoo.com/news/underground-tunnels-slideshow-wp-182540562.html