The Great Canary Telescope (Gran Telescopio CANARIAS; GTC), the world’s largest optical telescope has started its operation on July 13, 2007.
The huge observatory (with 10.4 metre telescope) is built atop a mountain on the island of La Palma (part of the Canary Islands); it cost $180 million and 7 years to construct. The GTC is doing test observations at the moment, with science observations intended to begin in about a year.