garden, park, orchard
园 centers on a cultivated enclosed space: a garden, park, or orchard where plants are grown and tended.
园 is the simplified form of 園. The older form 園 combines 囗 (enclosure) with 袁, which likely contributed the sound. The modern simplified form replaces the inner component with 元, which may serve as a phonetic or simplified substitute.
The enclosure 囗 surrounds 元 (origin, source). Picture a walled garden as the origin of fresh fruits and flowers, a park where nature begins.
For バン, imagine a garden with a big banner (バン) at the entrance: banner -> バン, and the garden is enclosed by walls.