York Minster is one of the great medieval buildings of northern Europe, and the interior rewards time spent rather than a quick circuit. The Great East Window contains the largest expanse of medieval stained glass anywhere in the world, spanning 78 feet. The undercroft museum shows the Roman and Norman foundations directly below the current floor, layers of occupation laid out clearly.
The tower climb (not for the unsteady) ascends 275 steps to a rooftop walkway with unobstructed views over the city walls, the vale of York, and on clear days the Moors and Wolds beyond. Separate ticket from the main entry. Do it if you can.