The main feature here is the wall, following the line of a river that splits two cities, one with a prominent skyline, the other built into the ravines below, choked with smog. Both seem to be a backdrop rather than anything truly accessible. It's a surprisingly vertical locale for someone who probably doesn't enjoy excessive amounts of stairs, but don't worry—there's a rusty lift that visitors can use to get inside (you can take equally rusty stairs, but also, why). Or, perhaps you'd like to explore below?
overlook
Visitors that choose to head upward into the wall find an interior full of machinery and the moving parts of what seems to be a water treatment facility. Following the flow of water leads to an overlook with a view out onto the houses and ravine. There isn't much else here, but if you need to contemplate your existence, or something, this is a good place to do it.
laboratory
Inside the wall, down a hallway, is the lab proper, an open space with high ceilings and plenty of room for wanton experimentation (the sky is the limit, and he is definitely blowing things up, sometimes on purpose). The room is configurable, with worktables and chalkboards sliding into place around a circular track, with Viktor's desk occupying a prominent space. The room is filled with various large-scale projects, and the formerly vacant work space that belonged to Jayce is empty once again.
the study
A room off the main lab houses Viktor's personal space, a workshop and study. It's much less professional and organized than the lab proper and generally more inviting, with a certain lived-in quality and various creature comforts: houseplants, plush furniture, shelves full of books, coffee pots, and a sunny, vaulted window that looks out over the city. Delicate clockwork projects are scattered across worktables and the walls and blackboards are covered in blueprints and notes. If Viktor isn't in the lab, he's likely here instead, and he doesn't seem to mind visitors, though when he isn't present in his domain, the door is locked. Leave a message.
fissures
Those who choose to explore below the wall find that there's a fairly straightforward path into the rocky crevasse. The water that flows through is unnaturally clear. One gets the sense that it's probably not this clean in reality, and is, instead, the result of a conscious decision to construct this place in a way that it could (or, perhaps, should) be.
the cave
The path of the water leads underground, into a cave entrance, which opens into a small grotto. There's a door built into the rock of the cave wall, but it doesn't open and the interior seems unoccupied. Visitors aren't alone down here, and may or may not be accosted by the weird dogwaverider-in-residence. Viktor will tell you her name is Rio like somehow this is the most normal thing in the entire world. You can feed her the purple flowers, if you don't mind some amount of monster slime. It's all fine.
???
Venturing even further into the cave system gives way to a complete structural breakdown, until the path forward ends and becomes seemingly endless fractals of criss-crossing purple webbing. Viktor doesn't seem to know it's here. You could stare at it for hours. Maybe you should leave.
addtl.
For anyone who has met Viktor outside of the Horizon, the difference may be slightly striking. Given the ability, he's done away with at least some of his physical impairments, maybe subconsciously, maybe not. He stands straighter and appears less exhausted. Instead of a crutch and leg brace, he uses a cane. Predictably, he feels no need to comment on this.