Nijo Castle - honmaru-goten or Ninomaru-goten?

We went to see Nijo Castle in 2014. It has been a while. We're going back to Japan and we remember loving the castle a lot and want to go again. However, I don't remember there being 2 palaces and I'm trying to figure out what the differences are? Which one has the nightingale floors and you can walk through?

TIA!