The park has been renovated. + We
used to play as kids in it.
(その公園は改修された。 + 子供の頃によ
くそこで遊んだんだよね。)
↓ 関係代名詞 which を使って1つの文にす
ると......
The park which we used to play as
kids in has been renovated.
(子供の頃によく遊んだ公園が改修され
た。)
↓ 前置詞 in を前に回して......
The park in which we used to play.
as kids has been renovated.