In Japanese, を is a particle that marks the object of an action. This means that the subject (the person or thing performing an action) is performing that action with the object being the goal/target of the action. In most cases, whatever を is attached to will not actually be ‘doing’ anything, but will instead have something being done to it.

• ラーメンを食（た）べる。
  To eat ramen.
• 歌（うた）を歌（うた）います。
  To sing a song.

In these sentences, を is marking the thing that is having an action performed ‘on’ it. This is how the Japanese language views the ‘object’. However, unlike English, an object can also be a place in which an action is performed ‘through’, if the goal of that action is based in that location itself.

• 公園（こうえん）を歩（ある）く。
  To walk through a park. (The park is the object that ‘walking’ is being performed through)
• 建物（たてもの）の中（なか）を走（はし）る。
  To run through a building. (The inside of the building is the object that ‘running’ is being performed through)

In these sentences, を is marking the place ‘through’ which the action is taking place. This use of を highlights that the place itself is what is being interacted with (running/walking requires interaction with the ground, so the ground/place is the object).