Canstruction is a charitable event aimed at putting a spotlight on the architecture, engineering and construction industries doing something tangible to help in the fight against hunger. The theme this year is The Spirit of San Francisco. Canstruction is similar to a sand castle contest, except these giant sculptures are made of canned food, typically using 3,000 – 5,000 cans per structure. The exhibition is then open to the public June 23 – 26. After the exhibit closes, the structures are dismantled and the cans are donated to the San Francisco Food Bank.