It's the central part of the Soviet Palace

The Palace of the Soviets (Russian: Дворец Советов, Dvorets Sovetov) was a project to construct a political convention center in Moscow on the site of the demolished Cathedral of Christ the Saviour. The main function of the palace was to house sessions of the Supreme Soviet in its 130-metre (430 ft) wide and 100-metre (330 ft) tall grand hall seating over 20,000 people. If built, the 416-metre (1,365 ft) tall palace would have become the world's tallest structure, with an internal volume surpassing the combined volumes of the six tallest American skyscrapers.^[​10]

Boris Iofan won a series of four architectural competitions held in 1931–1933 marking the beginning of a sharp turn of Soviet architecture from 1920s modernism to the monumental historicism of Stalinist architecture. The individuals behind these events and their motives remain a matter of conjecture and debate. Recent research supports the hypothesis that Iofan had been the chosen architect from the very start and manipulated the competitions to his own benefit.

因为苏维埃宫整体的完工还遥遥无期，就先把这个放出来吧（