The Brandenburg Gate has stood at the entrance to Berlin's heart since the late 18th century, when it served as the final gate before reaching Unter den Linden, a tree-lined boulevard that led to the imperial palace. It was also the center of the divide between East and West Germany during the Cold War and the site of U.S. President Ronald Reagan's famous 1987 exclamation: "Mr. Gorbachev, open this gate! Mr. Gorbachev, tear down this wall!" In 1989 the wall finally did come down, and the prime ministers from East Germany and West Germany met under the gate to shake hands for the first time.