The hilltop where VISTA is located was flattened to erect the enclosure building and an auxiliary building. The auxiliary building includes facilities to wash, strip, and coat the primary mirror. The coating can be in aluminium, or normally in protected silver for better infrared performance. The fixed base of the enclosure supports the rotating steel dome. Two sliding doors form the dome slit. Further dome panels can be opened to increase ventilation, and a wind shield can be deployed to close parts of the slit. During the day, the dome is kept at night-time temperature.