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 Diocletian (284–305), seems to have engaged in a substantial programme of rebuilding and of road construction from Ankara westwards to Germe and Dorylaeum (now Eskişehir). In its heyday, Roman Ankara was a large market and trading center but it also functioned as a major administrative capital, where a high official ruled from the city's Praetorium, a large administrative palace or office. During the 3rd century, life in Ancyra, as in other Anatolian towns, seems to have become somewhat militarized in response to the invasions and instability of the town. The city is well known during the 4th century as a