What is the largest-aperture Earth-based telescope currently in use at visible wavelengths?

Gran Telescopio Canarias

Explanation:

There are numerous giant telescopes all over the world which give us amazingly details data of the Universe. These work in various wavelengths. Talking about the telescopes which operates in visible wavelengths, the largest operational telescope will be Gran Telescopio Canarias. This telescope has an aperture of 10.4m. It is situated in Canary Island, Spain.

In future larger telescopes such as Thirty Meter Telescope and EELT will will make it look like a small telescope.