Cat urine is VERY pervasive and will make everything smell until it's addressed. To find it, purchase a portable black light from the hardware store.  When it's dark, use the light and it will reveal cat urine stains so that you can clean them.  Unfortunately however, if the urine stains are on the floor it could have seeped in too deeply to be cleaned, and instead, may need to be replaced completely.

For cleaning, you can try a product called "Nature's Miracle," or even simple white vinegar. Depends on the surface.