The National Observatory of Athens (NOA) is located atop the Hill of the Nymphs in the area of Thissio. This is the first research center in Greece and was inaugurated in 1846 by Baron Georgios Sinas.
Baron Georgios Sinas was a Greek consul in Vienna and national benefactor, with the donation of 500,000 drachmas to the Greek State and the assistance of Greek-Austrian astronomer George Bouris.
The institute’s scientific activity expands into astronomical, meteorological, cartographical and geodynamical measurements and observations. The main neoclassical building known as Sinas building was designed by Danish architect Theophilus Hansen, it has an iron entrance gate etched with the phrase "Servare Intaminatum" (def. "to be kept intact") and is one of the oldest and most renowned research institutes in Southern Europe. Next to the Sina building, a small building designed by Ernst Ziller houses a 16 cm meridian refracting telescope donated by national benefactor Andreas Syggros. Further to the south, a marble building houses the Doridis telescope a refractor with a lens of 40 cm in diameter and a length of 5 m, another donation by Dimitrios Doridis, a member of the Greek Diaspora, who left all his property to the Hellenic State when he passed away.
The National Observatory of Athens is conducting tours which must be booked in advance and are available in multiple languages, including English. There are special tours for elementary and high-school students. Limited evening tours for groups up to 25 people are also available upon request.