Cities XXL How to completely delete XXL/uninstall & reinstall as NEW

Hey all. I have come to the sad realisation that my game is probably corrupt. At one point in the last few months I was unable to create a new city at all the game would just crash, leaving me with only the one city that I have been working on for 2 years.

This of course was not a problem but when other issues started happening with my main city I decided for one reason or another to simply delete it all and then to reinstall via steam.

I thought I had deleted everything, however on first attempt it seemed brand new game, then after reopening it, old cities were there and after deleting them, now if I try to make a new city it again just crashes before it loads up the map.

The only thing I have carried over from the previous game install was the mods folder is there perhaps something in there not working with it I am unsure. I just want to be able to start afresh and need to know what exatctly to do to wipe everything from the computer/steam so that when I re-download its a new game with nothing carried over from previous.

Thank you.