This was the theory behind Canadian artist Peter von Tiesenhausen's decision to bury a sculpture almost four metres underground, beneath a sewer at the main crossroads in the city of Sarnia, Ontario.

BBC: Why make art no-one can see?

Mike Chinoy, a former CNN correspondent who has visited North Korea 15 times, said the current confusion about Pyongyang's capabilities recall a similar episode in 1998, when U.S. spy satellites discovered an underground complex at Kumchangri, not far from North Korea's main nuclear facility at Yongbyon.

CNN: 5 things we still don't know about North Korea's nukes

They chalked up their problems in the New York area to devastating flooding that, in addition to knocking out power, disabled backup generators and disrupted the underground cables that carry calls, texts and Web searches from cell towers back to the main networks.

WSJ: Outages Expose Wireless Carriers' Backup Plans