This week's episode of Game of Thrones gave us just a ~slight~ tease of the Tower of Joy.
Although we didn't get to see the rest of Ned's day, we did get this very interesting moment, when Bran seemed to be able to speak to his father in the past.
In the trailer for Season 6, we saw a brief clip of Bran, standing up, confronting the Night's King...who actually REACHES OUT AND TOUCHES BRAN'S ARM.
This has brought up an interesting theory: What if Bran is the cause of the Mad King's madness?
From S6E3, Bran realizes that others can hear him during the visions from the past, but doesn't understand that they cannot fully understand him.
He attempts to reason with King Aerys when shown a vision of him.
The King only hears whispers, and is driven mad by it.
Bran tries to fix this, however makes it worse.
Mad King Aerys burns Bran's grandfather alive while Bran frantically tries to stop him.
All he hears is whispers.
Bran sets the events of the show in motion.