Throughout Season 2 of Westworld, many of the characters have referenced a location called "the Valley Beyond." It seems like everyone, whether they are host or human, is trying to make their way to this place. But what is the Valley Beyond on Westworld?
Quite literally, it's Sector 16, Zone 4 of the park. That might not mean much to those who aren't experts at Westworld cartography, but at least it specifies that the Valley is a physical place. Unlike the maze, it's not just a metaphor for some higher state of consciousness. When Dolores first started using the phrase in the premiere of the second season, it seemed like it could be a more ephemeral idea; she debated who deserved to go to the Valley Beyond as though it were the next step in the journey, a reward for hosts she decided had earned it. It almost seemed to represent freedom or sentience. Now, however, it appears to be something much more tangible.
The Valley Beyond is still somewhat mysterious, but in "Les Écorchés" it became clear that it's tied into Delos' secret project and perhaps even the weapon William showed Dolores. And it might be somewhere viewers are very familiar with.
In Episode 7, Dolores stole an encryption key out of her former father's head. That key is connected to the Delos project that looks to resurrect human consciousness in host form, something that failed countless times when it was attempted with Jim Delos. It seems Dolores took that key to the Valley Beyond, because that was what Bernard reported to Charlotte after being interrogated. After hearing this bit of information, Strand remarked that they would have to go "back" to the Valley — which, as Vanity Fair pointed out, meant that they had been to the Valley before.
Many of the characters actually visited Sector 16, Zone 4 in the very first episode of Season 2. It was the flooded part of the park where Bernard was found alongside numerous drowned hosts. The Valley is where is all began this season and it seems like things are circling back around to the same location. Audiences may not have any idea what led to the flood (or to Bernard's declaration that he was the one responsible for killing all the hosts there) but it's the site of some seriously important events. Now it's where the key is, but luckily the Delos employees won't have to go diving to look for it: in Episode 1, it was announced that the Valley was being drained.
The Valley is also where young William took Dolores in "Reunion" to show her something she later described as a weapon she would use to destroy the humans. All the pieces are falling into place on Westworld even if they're not yet making a complete picture. The Valley seems to be very much linked to the plan to copy humans and turn them into hosts, so perhaps it's the site of a laboratory or a facility that houses all the guest DNA that was being collected. How Dolores will use that against the humans remains to be seen, though.
Dolores already did some damage in the Valley, and now Delos is heading there to try to find the key and salvage its data. But if Dolores went to all the trouble to destroy the Valley, then perhaps she also permanently ruined the key that everyone is so eager to get their hands on. She's promised nothing but destruction and seems intent on following through; if the key was still usable, it seems hard to imagine she'd just leave it behind. There may be some kind of trick or trap awaiting everyone in the Valley. It is a weapon, after all.