premise: Hayashi castle was a 15th-century castle, (alternatively known as Hayashi-jo, Fukuyama-jo) in Satoyamabe village, Matsumoto city, Nagano, Japan. A mountain-type castle, it is now largely in ruins. The site is sometimes regarded as one castle, or two castles, Hayashikojo (the small castle) and Hayashiohjo (the larger castle).
hypothesis: It's very hard to recognize that there was once a castle in Satoyamabe village.
reason: Because the castle lay largely in ruins and is so old, it could be easy to assume it is barely recognizable as a structure however nothing in the passage specifically states that it isn't recognizable, only that it lay in ruins. Many very old Greek structures are in ruins but can are easily recognizable as structures.