公園 and 広場: spaces and meeting points
Distinguish parks from open squares and separate an entire space from a specific place within it.
A park
公園, read こうえん, means park. 公園で散歩しました。 means taking a walk in a park.
公園の入口で待っています。 says that someone is waiting at the park entrance. Do not broaden this to an unspecified location anywhere inside.
An open space
広場, read ひろば, means square or open space. 駅前の広場に人が集まりました。 says that people gathered in the square in front of the station.
広場を横切りました。 means crossing the square. を marks the route, not an object that was moved.
One space within another
公園の中に広場があります。 says that there is an open square within the park. The two terms need not identify separate places.
広場の端で待ち合わせましょう。 proposes meeting at the edge of the square. Do not replace 端 with the center.
Where is the person waiting in 公園の入口で待っています?
Show the answer and why
At the park entrance, not at an arbitrary place inside the park.