The last wall of the final of the five buildings once used to enrich uranium at the former K-25 site will be demolished today. Demolition on the last building, the K-27 Building, started in February. The other four buildings—K-25, K-29, K-31, and K-33—were demolished between 2006 and 2015. All five of the huge facilities once used a process called gaseous diffusion to produce highly enriched uranium for atomic weapons and commercial nuclear power plants, starting during World War II and continuing through the Cold War. The largest was K-25, a mile-long U-shaped building. The former K-25 site in west Oak Ridge is now known as East Tennessee Technology Park, ETTP, or Heritage Center.