'The Maze' was the thematic centre of Westworld season 1, and having found his way to the centre of it, William was given a new quest in season 2, a quest to find "the door".

"You've made it to the center of Arnold's maze," the host version of a young Robert Ford told him in season 2 episode 1, 'Journey into Night'. "But now, you're in my game. In this game, you have to make it back out. In this game, you must find the door. Congratulations, William. This game is meant for you. The game begins where you end and ends where you began."

All sorts of theories about this door have been floating around the internet since, some suggesting it may be a more metaphorical one, representing the doors of perception, or to the past.

But nope, it is literally a big ass door.

Through one of the five billion flashbacks in Westworld we saw Ghost Nation leader Akecheta discover it in season episode 8, 'Kiksuya'. "A passage to another world" he described it as, before adding for the avoidance of doubt: "A door."

In an aerial shot, The Door could be made out on an outcropping, adjacent to a still-mysterious field of antennas.

It being a gateway to the real world chimes with what young Ford host said, the real world obviously being where William "began".

Is returning to the real world and facing the music, over his wife's suicide and the park's downfall, William's final challenge? Or is the door Akecheta glimpsed just a big red herring? More importantly, will Stubbs ever get a meaningful plotline?

Let us know your thoughts and theories below.

Westworld continues on HBO in the US and through Sky Atlantic and NOW TV in the UK.