From the Super Mario Wiki
Lenin's Tomb is the burial site dedicated to Vladimir Lenin. It is one of the landmarks in Moscow that gets attacked by Koopa Troopas in Mario is Missing!. Alongside the Moscow Metro, it is also exclusive to the DOS and Deluxe versions. The Koopa Troopas steal a Guard's Hat Pin from one of the soldiers protecting the tomb; this causes the entire location to be closed down. While visiting the city, Luigi takes back the Pin and returns it to the tomb's information booth, answering some questions about communism in the process, and lets Lenin's Tomb be reopened. The questions are as follows:
In 1917, Vladimir Lenin led the Communist revolution, which took power from the royal family and put it in the hands of the Communist party. Lenin became a popular hero. His tomb sits beside the Kremlin in Red Square. Although Russia is no longer a communist nation, the symbol of the old communist government decorated every public building, every official uniform and the Soviet Union's flag. That symbol was a crossed hammer and sickle atop a five-pointed star.