Buzludzha is a historical peak in the Central Balkan Mountains, Bulgaria and is 1,432 metres high. In 1868 it was the place of the final battle between Bulgarian rebels led by Hadji Dimitar and Stefan Karadzha and forces of the Ottoman Empire. The House-Monument of the Bulgarian Communist Party (also known as the Buzludzha Monument) was built on the peak by the Bulgarian communist regime. It commemorated the events of 1891, when a group of socialists led by Dimitar Blagoev assembled secretly in the area to form an organised socialist movement that led to the founding of the Bulgarian Social Democratic Party, a forerunner of the Bulgarian Communist Party. Construction of the monument began on 23 January 1974 under architect Georgi Stoilov, a former mayor of Sofia and co-founder of the Union of Architects in Bulgaria. The building exemplifies the brutalist architectural style common to many state-constructed communist buildings.