When Mark Zuckerberg said he planned to travel to all parts of the US to meet more Americans and learn about their lives, he wasn't kidding.
Zuckerberg on Wednesday travelled to a former gold mine -- located a mile underground in South Dakota -- that's now home to physicists and other researchers looking into things like neutrino particles and anti-matter.
"We're live from a mile underneath the earth's surface," Zuckerberg said during a video streamed to his Facebook page.
The Facebook CEO made the trip to the Sanford Underground Research Facility to champion the work of scientists and encourage more people to pursue research careers.
"I hope more people who are watching this think about going into scientific research," Zuckerberg said during the video, which has been watched by more than 1 million people.
The visit -- made via a roughly 10-minute elevator ride -- was also undertaken to highlight communities whose economies have been disrupted by globalisation.
"There are a lot of places that have had their economies focused on natural resources or on the land that are shifting to modern knowledge economies," Zuckerberg said, as he stood in what he said had been one of the world's largest gold mines.
The trip was part of what Zuckerberg in the video called his "year of travel," an effort to see all the US states he hasn't yet visited by the end of 2017.
Announced in January, shortly after President Donald Trump was elected and after what Zuckerberg had called "a tumultuous last year," the trip's goal is "to get out and talk to more people about how they're living, working and thinking about the future."
At the time, Facebook faced heavy criticism from those who said fake news on the site helped elect Trump.
The Facebook founder this week was clad in his usual attire of blue jeans, gray T-shirt and gray Nike sneakers with a black swoosh -- plus one extra item: A miner's helmet with a built-in lantern flashlight.
As the video camera rolled, he discussed the facility's experiments on matter and anti-matter with several scientists.
He also spoke with another worker there who had toiled at the site years ago when it was still a gold mine.
As he did, Zuckerberg noted the benefits that are possible in moving away from an industrial or agricultural-based economy.
"Rather than fighting over resources...with a knowledge economy that's not the case. You learn something new, you discover something and everyone can benefit," Zuckerberg said.