Do enlightened people "know" what nirvana is like? Do enlightened people "know" what nirvana is like? Obviously, they can't express it to anyone else, so the question isn't super helpful. I just wondered whether nirvana is a thing that we can know as well as experience or taste.

One response, one I don't (personally) want to hear about (at least without some in depth quotation) is that nirvana isn't "like" anything. And, of course, nirvana isn't similar to anything.

I'm asking whether Buddhas of any sort "know" the qualities (e.g. bliss) of nirvana.
Ud 8.1 says Nibbana is a sense object (ayatana) therefore it is obviously something known. 

MN 26 says:


  Then the thought occurred to me, 'This Dhamma that I have attained is
  deep, hard to see, hard to realize, peaceful, refined, beyond the
  scope of conjecture, subtle, to-be-experienced (vedanīya) by the wise.


SN 56.11 says:


  ‘This noble truth of the cessation of suffering has been realized (sacchikata).’
  
  
  
  Concise Pali English Dictionary sacchikata pp. of sacchikaroti
  realised; experienced for oneself.
  
  PTS Pali English Dictionary sacchikata seen with one’s own eyes,
  realized experienced


The Dhammapada says:


  205. Having savored the taste of solitude and peace (of Nibbana), pain-free and stainless he becomes, drinking deep the taste of the
  bliss of the Truth.


Nibbana is the dropping of all burdens; like the experience of relief when urgently urinating or dropping a heavy backpack or drinking cool fresh water on a hot day. 

Read more here: SN 43.14-43 and Nibbana For Everyone