I am looking for some old abandoned/ruined castle/fortified tower layouts.
Are there any available? I am terrible to draw layouts.
Did you try a search for "ruined castle floorplans" on the web?
There look to be quite a few, everywhere from the DeviantArt site to legit archives of game modules for various systems (and probably some not so legit).
In Ars maybe the Burg Pfalz from GotF? The floorplan for Triamore is sort of ruined, but more unfinished.
I did a little bit search. Deviant Art was a good source.
Thank you from help 
Search for floor plan generators as well. There's a couple of those...
Maybe you want to have a look at rptools.net/ as well.
Im sure there will be a couple more suggestions
an RPG blog called Dysons Dodecahedron has free maps which can be downloaded. He creates maps each week, has a patreon setup, and is darn responsive to comments and feedback. I've used many of his maps in games. See the /Maps subpage for a huge page of various maps.
e.g. Dravid’s Tower, and searching for "tower" on the page has 10+ results.
