And in case you have forgotten the last series and Christmas special, although much of those episodes were forgettable, here's a reminder
"Rageddy man... goodbye"
Now if you really want a some spoilers here's a video that takes the trailer and explains it. I love the idea of travelling within the Tardis. I always enjoyed the 1980s peeks into the Tardis. I loved the idea of rooms, wings indeed, a swimming pool, a library and more... There was the cloister room which is where the Eye of Harmony is locate which I think was the Tardis's power source.