Nature's Miracle works OK, there's another similar product called Urine-Off (I think) that worked better for me. We used to have a cat, and he peed on a section of an antique Persian rug several times before we noticed. Treated the stain probably six different times, soaking the product in and letting it air dry each time. Smell got fainter and fainter but would still come back on damp/humid days for several years after the cat was out of the house. Use a black light to find the affected areas and soak the hell out of them with whatever product you choose. Several treatments will be necessary to really clean, but the only thing that will make the smell go away is treatment + time.
That's why we don't have a cat.
That's why we don't have a cat.
