I sometimes prefer rooms without window. How can I find hotels in a given area that rent rooms with no windows? Do some accommodation search engines have such a filter?
I've never seen an explicit windowless room filter, and in many jurisdictions windowless rooms are against building code. But you can try your luck on Google Maps by searching for "windowless hotel", which finds reviews by people complaining about them!
One more place to look is the Yotel chain, which specializes in tiny rooms for short stays. Many -- but no means all -- of their rooms are windowless, particularly at their many "YotelAir" airport hotels.
And in Japan, virtually all capsule hotels are windowless, although the capsules are typically also doorless (there's a curtain instead) so they're not great if you want to isolate yourself completely.