Sukkah is a temporary, elemental shelter, erected for one week each fall, in which Jews gather to share meals, entertain, sleep, and celebrate Sukkot, the harvest festival. Biblical in origin, the sukkahs have traditionally been made with sticks and leaves and twine. A sukkah design competition called Sukkah City is being held in New York City, and 12 finalists have been chosen. The architects had to follow the Jewish law, which requires a sukkah to have at least three walls (two full and one partial) that can resist strong winds. By day the roof must provide more shade than sunshine. By custom it must also allow views of the stars at night. The 12 radically temporary structures are on display for two days in Union Square Park.