Lincoln Cathedral
countrylife.co.uk
countrylife.co.uk
There is, of course, the "stump" at Boston too which inspired one of Yale's towers: https://en.wikipedia.org/wiki/St_Botolph%27s_Church,_Boston
https://en.wikipedia.org/wiki/History_of_the_world%27s_talle...
https://en.wikipedia.org/wiki/St_James'_Church,_Louth?wprov=...
https://en.wikipedia.org/wiki/List_of_tallest_church_buildin...
There are plenty of other reasons to visit the castle though, including the (very much active) courtroom and (no longer active) prison, or just to walk along the battlements for the view.