Strong cat urine smell not budging

[Alissa Mait]

I am hoping to buy a condo in a high-rise building. The recent renter had a cat that must have been urinating on the floors the past few years. The smell is incredibly strong. The current owners have cleaned and treated the carpet and travertine flooring twice with zero success/change. I'm planning to remove and replace carpet/padding anyway, but wondering if I'll have to do the same for the flooring (which will be quite expensive. My biggest worry is that if I do remove and replace travertine, perhaps the floor under the travertine has also absorbed urine crystals and will continue to smell even with new flooring. I also worry that the urine/crystal are in the walls and maybe even ceiling since cats sometimes spray. Does anyone have experience with long-term cat urine damage despite removing and replacing floors and carpeting? Thanks very much for any help/advice/ideas! Alissa