Ankara Treaty of Lausanne (1923), the Turkish nationalists replaced the Ottoman Empire with the Republic of Turkey on 29 October 1923. A few days earlier, Ankara had officially replaced Constantinople as the new Turkish capital city, on 13 October 1923. After Ankara became the capital of the newly founded Republic of Turkey, new development divided the city into an old section, called "Ulus", and a new section, called "Yenişehir". Ancient buildings reflecting Roman, Byzantine, and Ottoman history and narrow winding streets mark the old section. The new section, now centered on Kızılay Square, has the trappings of a more modern city:
Ankara University Observatory Ankara University Observatory The Ankara University Observatory (AUG) (), is a ground-based astronomical observatory operated by the Astronomy and Space Sciences Department at Ankara University's Faculty of Science. Established in 1959 by Dutch astronomer Egbert Adriaan Kreiken in Ahlatlıbel, Ankara. Currently, it consists of nine optical telescopes and a radio telescope, which is currently taken out of service. Old instruments are displayed in a museum at the observatory. Ankara University's Faculty of Science decided in 1954 to establish an observatory to begin with astronomical studies. Ahlatlıbel in Gölbaşı, Ankara was chosen as the ideal site, a location with dark skies