Knick-Ei was the nickname of a sports hall located at the corner of Feldstraße and Bahnhofstraße in the city of Halstenbek, located in Pinneberg county in the state of Schleswig-Holstein in northern Germany. The nickname refers to the hall's dome-shaped roof which collapsed twice during construction. The sports hall was never operational and was eventually demolished in 2007. The building's official name was "Sporthalle Feldstraße".