This is one of Dionysus' favorite rooms, to the point that he's reasonably convinced he has to be the one who willed it into existence in the first place. It's perfect for all sorts of parties, and when he hasn't cleared it out for an event, it is full of comfortable places to sit or lie down. It was the main source of all the cushions he took to his room when he was first decorating it, back shortly after he arrived. He makes himself comfortable now, because he knows where the card is hidden (camouflaged in a pile of similarly-colored cushions) and anticipates it being a while before Grantaire finds it.

When he does find it, it says,
Where you gave me my stars, and where I get to wake up beside you nearly every morning.