The hidden Doors of My house

"I was walking through my house like normal, but then I noticed a door in the hallway that I'd never seen before. I opened it and there was a whole extra room, bigger than it should have been, with a couch and a window looking out somewhere I didn't recognize. I went back to the hallway and found another door behind a bookshelf. That one led to a narrow staircase going down, and at the bottom there were two more rooms. One was full of old furniture, and the other had a desk with papers all over it, like someone had just left in the middle of something. I remember feeling excited, like I'd found part of my house I didn't know existed. I kept thinking I should tell someone, but I also didn't want anyone else to see it yet. Then I woke up, and for a second I genuinely thought there might be a door behind my bookshelf."