Help needed - Removing Cat pee smell from concrete

One of the biggest challenges with this move is trying to get rid of the cat pee smell from the concrete in the basement. This is made worse by the fact that someone insists on continuing to pee on it. Access to this has now been blocked, the litter has been moved.

Any suggestions on how to get the smell out? We have tried a lot of things but nothing has really worked. The internet has lots of ideas, but I was wondering if anyone out there had tried something that worked.

Thanks!