に置いてある

is placed in/on; has been left in/on

→ に
phrase Rare #29,396
is placed in/on; has been left in/on Describes something that someone has placed and that remains in a particular location. The particle に marks the location, while 置いてある indicates the resulting state. The exact term usually appears before the noun it describes or at the end of a sentence.
JA: あそこに置いてある自転車は弟のよ。
EN: The bicycle that is parked over there belongs to my younger brother.

あそこに置いてある自転車は弟の

The bicycle over there belongs to my younger brother.

お店に置いてあるはまだ誰のでもないって

“The things in a store don’t belong to anyone yet,” they said.

— 万引き家族 (2018)

政府の極秘地図を部屋に置いてあるのか

Are you keeping the government's top-secret map in the room?

— イングリッシュ・ペイシェント (1996)