I went to see Sakura(cherry blossoms) in Shinjukugyoen (新宿御苑) whish is huge and histrical park in Shinjuku ward in Tokyo. Here is about Shinjukugyoen.
Shinjukugyoen has 58.3 ha and the perimeter is about 3.5 km. Here is the map.
It was clowdy when I went there, but Sakura bloomed beautifully.
It was a garden for the Imperial Household, but became national park after war.
I think Japanese people are most crazy nation for Sakura.
People love to just watch and do Hanami party under the trees.
You can get in the part at 200 yen for an adult. I think sports stuff is not allowed, but you can lay down on the ground and relax, and even lunch :)