

The most powerful telescope is the newly constructed 40 m telescope which was completed in 2005 and saw first light in ¿May 2007?. The Technological Development Centre (CDT) facilities include two radio telescopes, a solar tower, an astrograph and a Gravimeter. The wind velocity is generally below 5 m/s for most of the year, and the occurrence of rainy or snowy days is less than one week annually.

The precipitable water vapor (PWV) level remains below 6 mm, dropping to a minimum of 2 mm during winter. It is located at an altitude of 931 meters above sea level and benefits from exceptional observing conditions throughout the year. The observatory is located around 50 kilometres (31 mi) to the North-East of Madrid in the province of Guadalajara in the autonomous community of Castilla-La Mancha. Yebes Observatory is the main scientific and technical facility of the National Geographic Institute of Spain. The telescope is located at Yebes Observatory (Spanish: Centro Astronómico de Yebes (CAY)).

It is a 40-metre Cassegrain–Nasmyth telescope. The Yebes Observatory RT40m, or ARIESXXI, is a radio telescope which is part of the observatory at Yebes, Spain.
