Always never easy and even less so if we don't know your wives taste or how much you want to spend, but something I'd say you can absolutely never go wrong with is a nice trip somewhere you can both enjoy, maybe invite some surprise guests along as well that arrive later, maybe friends of yours you haven't seen in ages, where they suddenly pop up behind her at pre-dinner drinks, etc.
Or a watch is probably something usually pretty welcome too, jewelry you can't necessarily always wear every day, but with a watch it doesn't matter what it is and you normally can.
Or maybe she's always hinted at wanting to do something one day, eg take a photography course or whatever her thing is, and you organise such a course for her together with whatever she'll need, nice camera in this case.
Just some ideas.
🙂