A park is a big box full of earth, that extends from here to far away.
park ★★★★★ 公 (public) + 園 (public park) = 公園 (park)
a public park
zoo ★★★★☆ 動物 (animal) + 園 (public park) = 動物園 (zoo)
amusement park ★★★☆☆ 遊 (play around) + 園 (public park) + 地 (area) = 遊園地 (amusement park)