Despite the witty, sarcastic humor of the writing, digging beneath the surface of Portal will reveal a world of deranged insanity. Trust us, Aperture Laboratories isn't all sunshine and daisies.
- The areas behind the platforms when you go off the rails and see the scribblings of former employee Doug Rattmann become unnerving. This guy has clearly slipped into insanity, and he even knows that at the end, you'll just be met with an agonizing death by burning, and to top it all off, you can see exits just out of reach, and nightmarish music plays in the background.
- The last three levels of the game have you going inside Aperture. The dim, occasionally flashy lighting, the occasional turrets, the writing on the walls...
- In Chapter 3, Testchamber 17 you can discover a hidden chamber: "Fear the turret for it is knell, that summons to heaven or to hell." There's a picture of Chell sleeping there, but she looks dead. Then once you leave the hidden chamber, the opening closes, and so does the door to the office looking over your test chamber. It's almost like someone watching you. Additionally with some careful shooting, when you get the Hard Light Bridge to lead you to the observation room, you can get a portal into the hallway. Go in and there is no one there. There's also a door that leads to the Rattman den and you can't get it to open from either side. And when you're in the den, you can still hear his voice (the soundtrack calls the "Ghost of Rattman", giving the whole area a bit of a haunted vibe.
- Most of the songs in Portal 2 Soundtrack [Songs to Test By] are fairly great, both in action and ambiance but "Overgrowth" in particular stands out for being very low and eerie and just produces a sense of dark dread. The rest of the early chamber tracks sound relatively upbeat in comparison.
- The core transfer scene. Hearing GLaDOS scream in pain as her face gets ripped off is horrifying, and then Wheatley slowly succumbing to the chassis's power... The imagery of the transfer device pit as a portal into hell with fifty little claws and devices reaching up at her didn't help, especially as the sound file for GLaDOS' scream is called "sp_a2_core_drag_to_hell01.wav."
- Although some interpreted it as a Mercy Kill, some players found it creepy when GLaDOS coldly deletes Caroline right after admitting that she's the voice of her conscience. Not helped by the fact that a flatline can almost be heard after the deed is done.
- ALL of the Rattmann Dens in the second game are really creepy. The broken lighting, the discomforting music, the pictures, all of it. But the scariest has to be in the den where you complete the Final Transmission achievement...
- The menu music in chapter 6. So you spend several hours in Aperture's massive creepy parts, then you decide to take a break and quit the game and you're hit with that eerie, creepy magnificence. There's a reason why that piece of music is called "PotatOS Lament" on the soundtrack.
- One of Rattman's murals shows a woman, screaming with the most horrifically drawn face, as several scientists die around her. The woman is implied to be Caroline. To make it worse, you can also see in the lower right corner of the mural what seems to be Rattmann begging for mercy or hiding behind a companion cube.