a powerful group of Communist republics (= countries without a king or queen) including Russia, Belarus, Ukraine, Georgia, and 11 others that existed in Europe and Asia from 1922 to 1991

The Soviet Union was one of the most centralized regimes in the world. 苏联是世界上最集权的政权之一。

The Kremlin in Moscow is the final resting place of most leaders of the Soviet Union. 莫斯科克里姆林宫是苏联大多数领导人的最后安息之地。