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:
Sanjak of Ankara capital, and after 1852 the province was once more known as the Ankara Eyalet, and after 1867 as the Ankara Vilayet. In 1912, the "sanjak" of Ankara comprised the districts ("kazas") of Ankara proper, Ayaş, Beypazarı, Nallıhan, Mihalıççık, Sivrihisar, Haymana, Bala, Yabanabad and Kalecik. Sanjak of Ankara The Sanjak of Ankara was a second-level province ("sanjak") of the Ottoman Empire. The town of Ankara became part of the Ottoman state in 1361 or perhaps in 1354. It was the first capital ("pasha sanjak") of the Anatolia Eyalet from its formation in the late 14th century until the late 15th century,