The Gran Telescopio Canarias (GTC) is the largest optical telescope in the world, with a primary mirror diameter of 10.4 meters.

The Paranal Observatory is located in the Atacama Desert in Chile and is home to the Very Large Telescope (VLT), one of the most advanced optical telescopes in the world.

The Mauna Kea Observatories are located on the summit of Mauna Kea in Hawaii and are home to some of the largest and most advanced telescopes in the world, including the Keck I and Keck II Telescopes.

The Kitt Peak National Observatory is located in the Sonoran Desert in Arizona and is home to a variety of telescopes, including the Mayall 4-meter Telescope.

The La Silla Observatory is located in the Atacama Desert in Chile and is home to a variety of telescopes, including the New Technology Telescope (NTT).

The Siding Spring Observatory is located in New South Wales, Australia and is home to a variety of telescopes, including the Anglo-Australian Telescope.

The South African Astronomical Observatory (SAAO) is located in Sutherland, South Africa and is home to a variety of telescopes, including the Southern African Large Telescope (SALT).

The Aryabhatta Research Institute of Observational Sciences (ARIES) is located in Nainital, India and is home to a variety of telescopes, including the 3.6-meter Devasthal Optical Telescope.

The National Astronomical Observatories of China (NAOC) is located in Beijing, China and is home to a variety of telescopes, including the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST).

The Subaru Telescope is located on Mauna Kea in Hawaii and is operated by the National Astronomical Observatory of Japan (NAOJ).

The Special Astrophysical Observatory (SAO) is located in Zelenchukskaya, Russia and is home to a variety of telescopes, including the 6-meter BTA-6 telescope.

The Royal Observatory Greenwich is located in London, England and is home to a variety of telescopes, including the 28-inch refractor telescope.

The Observatoire de la Côte d'Azur is located in Nice, France and is home to a variety of telescopes, including the 3.6-meter Canada-France-Hawaii Telescope (CFHT).

The Max Planck Institute for Astronomy is located in Heidelberg, Germany and is home to a variety of telescopes, including the 2.2-meter MPG/ESO 2.2-meter telescope.

The Osservatorio Astrofisico di Arcetri is located in Florence, Italy and is home to a variety of telescopes, including the 1.8-meter Galileo Telescope.