The Giant Magellan Telescope (GMT) is a ground-based extremely large telescope planned for completion in 2020. It will consist of seven 8.4 m (27.6 ft) diameter primary segments, with the resolving power of a 24.5 m (80.4 ft) primary mirror and collecting area equivalent to a 22.0 m (72.2 ft) one, (which is about 368 square meters). The telescope is expected to have over five to ten times the light-gathering ability of existing instruments. Three mirrors have been cast and the mountain top is being prepared for construction.