Kurtuluş Şavaşı museum, the museum of the War of Independence. It housed the first sessions of the Grand National Assembly, before it moved over to the museum some hundreds of meters down the road. Before that it was the Ankara headquarters of the Committee of Union and Progress, the political party which in 1909 overthrew Sultan Abdülhamid and attempted to bring democracy to the Ottoman Empire (quotes from Lonely Planet Guide).
Inside photography was forbidden. Not much of a loss, the displays were rather mediocre, with the exception of the room where the first meetings were held. A ticket for this museum is valid for the other museum too.