。
A bystander can see most of the game.
Literal
Bystander [dat-に] [topic-は] game [possessive-の] most [subject-が] can-be-seen
Note the double particle には — the dative に marks the bystander as the experiencer ('to a bystander'), and は topicalizes that phrase. みえる is the spontaneous/potential form — 'is visible', 'can be seen' — not the volitional 見る. Used here to mean 'a bystander has a view of most of the game'.