Advanced Computation Building / ACB
The Advanced Computation Building was designed by Clark, Altay and Associates and with its groundbreaking on October 15, 1969.  Originally built to house one of the early supercomputers, it became the home of the Astronomy Department immediately upon completion in 1971,  before becoming the central machine room of the National Center for Supercomputing Applications.
On June 9, 2000, work began on an addition to the building to house the Center's new generation of superclusters. The 18,029 square foot addition is 97 feet long by 95 feet wide and has an electrical capacity of 2,500 KVA. 
One interesting architectural aspect of the building is the glass ceiling of its elevator. Rumor has it that the glass ceiling was put into place during the Vietnam War so that security personnel could check for intruders in the elevator shaft. In fact, the real story behind the ceiling dates back to the Astronomy Department's tenure in the building. The astronomer's, wishing to gaze upon the stars during their daily commutes in the elevator, had the top of the elevator shaft converted into a transparent skylight, allowing them to look straight up to the sky. However, after a number of years this skylight began to leak and was eventually replaced with a corrugated metal cap.