We saw it from miles away, sitting atop the crest of a hill. the old walls were crumbling, but you could still see the outlines of the vast parapets and stone towers.

the author is most likely looking at

an old house.
an old castle.
an old mansion.
an old building

B) An old castle.

Explanation: In the given excerpt we can see the description of something the speaker is looking at, it is at the top of a hill, it is some kind of building because it says it has walls, and we know it is old because the walls are crumbling and it says "old walls." By the description of the structure having still visible outlines of "vast parapets and stone towers" we can infer that the author is most likely looking at an old castle.  

B) An old castle.

Explanation: In the given excerpt we can see the description of something the speaker is looking at, it is at the top of a hill, it is some kind of building because it says it has walls, and we know it is old because the walls are crumbling and it says "old walls." By the description of the structure having still visible outlines of "vast parapets and stone towers" we can infer that the author is most likely looking at an old castle.  

needs an explanation