The 1876–77 Constantinople Conference (Turkish: Tersane Konferansı "Shipyard Conference", after the venue Tersane Sarayı "Shipyard Palace") of the Great Powers (Austria-Hungary, Britain, France, Germany, Italy and Russia) was held in Constantinople (now Istanbul) from 23 December 1876 until 20 January 1877.
Text from Wikipedia, licensed under CC BY-SA 4.0
The 150th anniversary falls on December 23, 2026.