La Silla telescopes. At upper left is the dome of the 3.6 metre telescope, the first large telescope built by the European Southern Observatory (ESO). At lower right is the 15 metre diameter dish of the Swedish-ESO Sub-millimetre Telescope (SEST), a type of radio telescope. Many ESO facilities at La Silla are being closed as they relocate to Cerro Paranal, the home of ESO's Very Large Telescope, several hundred kilometres to the North. La Silla is in the Chilean Atacama Desert, where high altitude (2400 metres) and very dry air make for excellent viewing conditions.