The Very Large Telescope (VLT) at Cerro Paranal is ESO's premier site for observations in the visible and infrared light. All four unit telescopes of 8.2-m diameter are individually in operation with a large collection of instruments.
The VLT offers also the possibility of combining coherently the light from the four UTs to work as an interferometer. The Very Large Telescope Interferometer (VLTI), with its own suite of instruments, ultimately providing imagery at the milli arcsecond level as well as astrometry at 10 micro arcsecond precision. In addition to the 8.2m diameter telescopes the VLTI is complemented with four Auxiliary Telescopes (AT) of 1.8m diameter to improve its imaging capabilities and enable full nighttime use on a year-round basis.
Two powerful survey telescopes - the Visible and Infrared Survey Telescope for Astronomy (VISTA) and the VLT Survey Telescope (VST) - are also part of the ESO's Paranal observatory.
Detailed information for each of the instruments on the VLT and VLTI can be found via the Paranal Instruments menu.