Tom Hanks is used to perplexing his fans on Twitter.
The Hollywood star regularly posts photographs of random lost gloves and other items of clothing that he spots discarded on the street.
On Friday, however, he freaked out many of his 13 million followers with this snap of a building in New York City:
"This is the scariest building I've ever seen," wrote Hanks of the windowless edifice. "WTF goes on inside??"
His question prompted plenty of speculation:
Amid the lighthearted suggestions, however, some fans actually attempted to answer Hanks factually.
While the building at 33 Thomas Street in Lower Manhattan is technically owned and occupied by AT&T and Verizon, it's reportedly used as the National Security Agency's spy hub.
So now Hanks knows.