#BBCtrending: Twitter treasure hunt in San Francisco
An anonymous tweeter in San Francisco has been hiding dollar bills around the city and posting pictures of their location to help people find them.
The first tweet - a picture of a vegetable patch - appeared on Friday. Since then, pictures of money hidden under plant pots, benches and parking meters have been posted, each with a clue as to their location. Sometimes the money is tucked away with only a famous landmark to suggest its whereabouts. The city's famous Golden Gate Bridge and Palace of Fine Arts have both featured in the game.
Each new message prompts people to search for the money, usually around $100 (£60). After just five days the account the @HiddenCash Twitter account has more than 120,000 followers, and as news of the game has spread, people who have located money have begun posting pictures of themselves clutching their find at the chosen spot.
San Francisco resident Forrest Hanson told the BBC's Newsday he found the money after a new picture showing the city's iconic bridge was published. "My friend and I jumped in our car and headed to Baker Beach, just West of the Golden Gate Bridge," he said. "There was a bridge, and a fence, and this bit of shrubbery... I happened to toe my foot in the sand in the right spot."
Hanson decided to return the gesture of goodwill, and offered the the money to two families who had children. "We figured this was already a good time for us, so we gave the money away," he says.
The person behind the account is believed to have made a fortune in the property market, and claims the project is "an anonymous social experiment for good". "There is nothing wrong with donating money to a traditional charity, but I also wanted to donate in a more spontaneous way," he told People magazine. "I want this to expand to other cities. I want this to become a movement," he said.
All our stories are at BBC.com/trending