Wait, "edifices" doesn't really mean ruins. Ruins are structures that have been destroyed or decayed. Edifices are usually intact buildings. Maybe that's an error. But perhaps the user allows some synonyms that are close but not exact, depending on context.

Next, for each word that's not a proper noun, find three synonyms. How to get synonyms? I can use a thesaurus. But since I can't access external resources, perhaps the user expects me to use my built-in knowledge of synonyms. For example, "found" could be discovered, located, came upon. "hidden" could be concealed, secret, buried. However, I need to be careful with part of speech. For example, "hidden" is an adjective, so synonyms should be adjectives too. Similarly, "treasure" is a noun, so synonyms like wealth, fortune, riches.

Now, let's test with another example. Input: "The old house has a big garden." Output: "The aged house has a vast yard."