Shinjuku Gyoen (新宿御苑) is one of the largest parks in Tokyo and a popular spot for viewing cherry blossoms, as the large crowds can attest to. I was lucky enough to arrive in Tokyo at the start of the cherry blossom peak and see the blossoms.
The park is close to Shinuku Station, just follow the crowds if it's during sakura season. Entry is 200 yen.
