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The Gran Telescopio Canarias is a 10.4 m (410 in) reflecting telescope located at the Roque de los Muchachos Observatory on the island of La Palma, in the Canary Islands, Spain. It is the world's largest single-aperture optical telescope.
Image: H. Raab (User:Vesta), CC BY-SA 3.0 · Text from Wikipedia, CC BY-SA 4.0