Portal 2 - Act 5 Menu Theme (1 Hour Loop, 4K)
Main menu screen for Portal 2 titled "Act 5". I think it's somewhat difficult to avoid this spoiler on the internet when discussing Portal 2, but for what it's worth to remain spoiler-free, it only appears after listening to a mini opera concert.
Ripped from game files and upscaled to 4K using video2x