On Paranal ESO operates the ESO Very Large Telescope (VLT) with four 8.2-m Unit Telescopes (UTs). Each UT can work independently, in which case it sends the light beam towards either a Cassegrain or one of two Nasmyth focus stations for facility instruments. In addition, the UTs can work together to form an interferometric array (VLTI): in this case, they send the light beams towards their Coudé focus station, where adaptive optic systems correct the light beams for atmospheric turbulence before forwarding them to an interferometric laboratory to be coherently combined.
ESO also operates four 1.8m Auxiliary Telescopes (ATs) which form the VLT interferometer small array (VISA).
Currently, 14 instruments are operational and offered for science observations. The 15th instrument to be offered to the community as of P98 will be Gravity at the VLTI. Furthermore, ESO also operates two survey telescopes, each with its own instrument: the 4-m infrared VISTA, and the 2.5-m visible VST.