I've seen a few good Ikea hacks where people have successfully hidden their litter boxes (examples here), so I've been working on my own for a while. Our cats are very upright-facilitators, so we needed some piece of furniture that was quite tall, and the only space in the apartment that was available was the narrow area behind the front door, so it took a while to find the right bit of furniture for the job, but I think we did! It's actually a drawer unit from Ikea, designed to hold your PC. Fits perfectly behind our door and I found a plastic tub that slides in. The glossy white finish matches our decor (as much as we have decor right now), so I'm very pleased. Just debating on whether or not to fuss with hanging a fabric curtain or some other cover over the entrance or not. Thoughts?
Entryway before and after (please note that the tidy 'after' photo is totally staged, I expect this area to be total chaos within a day):

That's great...can barely tell what is in there!
Very clever! Do they mind being in a high(ish) traffic area?
I think it's probably better left as is - your look is pretty sleek and a curtain might look cluttered. Also the cats might not like it, and you know who's boss! :)
Thanks for the feedback - and yes, they are totally the bosses. :)
They don't mind being there - they seem pretty flexible - we've had different arrangements in the 3 apartments they've lived in and they never fussed.
I'm quite pleased with it - we've even avoided covering the top with clutter so far.
I think that is brilliant! And agree, I don't think it needs a curtain, you can't even tell it IS a litter box, and a curtain would just add clutter to the space I think.