Kremlin

Kremlin is Russian for fortress and would be the equivalent of castle in English. Since the 1920s, it has become a metonymy for the Russian government in the same way as Westminster is for the British government. There has been a fortress or castle in Moscow since the 1300s at least and the existing walls of the Kremlin were built in the 1400s. Most of the current internal structures were re-built in 16th and 17th centuries by the Russian Tsars.