Greetings @Ayekayybayy!
I noticed that you had posted the same question in your Dreams…feathers post, so I hope you don’t mind that I combined the two threads to keep everything together and easy to access 
As for reading dreams, others may disagree, but I personally don’t think every dream has magickal significance (more about my stance on reading dreams here). That being said, I do believe that dreams that occur over and over again are a sign that something is trying to get your attention- it is likely that the dream will continue to repeat until the issue has been confronted and resolved.
That’s a very good sign for your friend. If the dream was warning about some impending doom or horrible thing, it is very likely that those emotions would come through in the dream. If your friend doesn’t feel bad or fearful during the dream, then I think it is unlikely it is foretelling doom or danger.
My best guess is that something (be it his deeper conscious, the Universe, a diety, etc) is trying to tell him something. Since the dream has been happening for years, it is likely something very important for his personal growth and life path.
I would recommend that your friend consults a method of divination, and preferably one that can give advice and guidance (such as tarot or tasseography). Methods that give primarily yes/no answers (such as pendulum readings) will probably not be as helpful here.
The mention of temples/ruins makes me think that another thing he could look into, if it is in line with his beliefs, is his past lives (more info about past lives here). What is happening now could be something that happened in a previous life that is influencing or affecting his current dreams.
Wishing all the best to you and your friend, Krysten! Blessed be 