Since they don't know the shit is hitting the fan all around them, Rory asks River about the "worst day" thing she cryptically said before, and this part is sad -- especially if you ignore the distracting bit where the entire River Song thing is being rewritten right in front of you, invalidating whole swathes of previously established continuity: "When I first met the Doctor, a long, long time ago, he knew all about me. Think about that. Impressionable young girl, and suddenly this man just drops out of the sky [note for later]: He's clever, and mad, and wonderful, and knows every last thing about her. Imagine what that does to a girl."
Rory doesn't have to, because of Amy. Also because of every other Moffat episode and female character.
"Trouble is, it's all back to front. My past is his future. We're travelling in opposite directions. Every time we meet, I know him more, he knows me less. I live for the days when I see him. But I know that every time I do, he'll be one step further away. And the day's coming, when I'll look into that man's eyes -- my Doctor -- and he won't have the faintest idea who I am. And I think it's going to kill me."
Very moving, and sad. I mean, that's about as retconny as the Weeping Angels thing, and we already know how she dies, but also consider the fact that their relationship still hasn't happened, from our perspective. He hasn't given her the shiny fabulous screwdriver, they haven't actually been in love, or gotten married... I suppose that it could be in the 200 years between 908 to 1103, given that this is the most romantic they've ever gotten on the show that would make sense for what comes next and we wouldn't have to waste the onscreen time of constant meaningless cool shit seeing it happen. I don't know.
They walk into what appears to be a dead ringer for the DIY TARDIS from "The Lodger," to which reference will always earn a few extra points because that episode rocked so hard, and Rory notices and immediately forgets noticing that the room they've found is covered by about a million Silence. River somehow notices that the tunnels extend under the entire surface of the world, and then yells Rory's name when she finally notes the monsters that are all over the place: Cliffhanger 1.