This is a good place to start if you want a refresher course on Soviet history. Originally built by Giliardi in 1787, the mansion was rebuilt in the classical style after the Moscow Fire of 1812; it was once the social center of the Moscow aristocracy and its entrance is flanked appropriately by two smirking lions. The building housed the Museum of the Revolution from 1926 to the late 20th century, at which time the museum was converted to its present purpose. Although
the museum retains many of the former exhibits—heavily imbued with Soviet propaganda—they have been updated to reflect the changing political climate in Russia. The permanent exhibit, on the second floor, begins with a review of the first workers' organizations in the 19th century. The exhibits outlining the 1905 and 1917 revolutions include the horse-drawn machine-gun cart of the First Cavalry Army, the texts of the first decrees of the Soviet government on peace and land, dioramas and paintings portraying revolutionary battles, and thousands of other relics. The next rooms outline the history of Soviet rule, with extensive material devoted to Stalin's rise to power before whizzing through the short post-Soviet history.
With a huge archive and the country's best collection of political posters and medals, the museum has a reputation for hosting excellent temporary exhibits. Explanations are only in Russian, but you can arrange a tour in English by calling ahead. The fine gift shop sells Russian souvenirs (including some beautiful amber) and great vintage items like flags and political-rally posters.