Jewel, the reason your cat is going back to the same place is because it's highly sensitive nose can still smell the urine even if you can't. You need to clean the area with something the breaks down the protein in the urine. If you have money to spare, then you can head to the vet and pick up a spray that does the job for you. But if you want to go a cheaper option, then head to the supermarket and buy some BioZet clothes washing detergent. BioZet contains enzymes that breaks down the protein in the exact same way that the vet spray does (there are other brands that have the same enzyme action, but I couldn't guarantee which ones...). Mix some BioZet with water to make a big of a slurry and work it into the carpet and leave for a little while. Then rinse the area as well as possible to remove the detergent (just like you would with any cleaning product you would use). We've always recommended this at the Vet Clinic I worked at before I had DS and everyone has always been amazed at the results