The telescope of National Observatory of Athens named "ARISTARCHOS" is the largest telescope in the Balkans and the second largest in mainland Europe, and is located on top of "Neraidorahi" Helmos at an altitude of 2340 meters near the ski resort of Kalavrita.

This location was chosen due to the fact that it is one with the lowest light pollution in whole Europe and the telescope is over the hight of clouds. The first steps and first draft designs were in 1997. Its construction began in 2001 and August 20, 2007 inaugurated and handed over officially to the scientific community.
The telescope "Aristarchos" is considered one of the most technologically advanced telescopes in Europe. It has a diameter of 2.3 meters and great targeting precision and celestial tracking of objects. The telescope serves educational scopes by training students locally or via network or public education as schools, universities, cultural institutions, etc., or for scientific and technological services of high quality educational and social organizations. 

Sources
National Observatry of Athens 
Institute of Astronomy and Astrophysics
www.astro.noa.gr

source: http://el.wikipedia.org , www.kalavrita.gov.gr