San Francisco's Potrero Hill neighborhood is home to hilly streets, views of the Bay Bridge—and the Crypto Castle, a three-story home where a half dozen cryptocurrency entrepreneurs live and collaborate. Jeremy Gardner is a co-founder of the Crypto Castle, initially both a home and the headquarters of start-up Augur, a decentralized prediction market platform. "We didn't have the money for all the salaries to pay everyone to go live on their own so it was much cheaper to keep everyone in one place, eradicate housing costs and still be in San Francisco," said Gardner.

From there the house grew, with a rotating cast of crypto-currency entrepreneurs as tenants, and became a crash pad for visitors. Self-driving car start-up Comma.ai was created in the basement, with CEO George Hotz living in a closet right off the main room. Eventually, the company raised several million dollars in funding, and he moved out. Gardner said one of his "favorite nights" happened when Ethereum creator Vitalik Buterin was crashing there and got into discussions with BitTorrent founder Bram Cohen. "Those collaborations are a plenty here which is really probably the best part." Beyond the collaborations, there is a sense of community not unlike the hippie communes that San Francisco was once known for.

A group of people attend a party in the early days of the Crypto Castle