Whether it was blowing a wall away in the original Zelda or stumbling through into Warden Sharp's office in Arkham Asylum, there's something about finding a secret level no one else has discovered that makes exploring a game world endlessly entertaining.
Developers like Rocksteady and Rockstar revel in the inevitable easter egg hunts that surround any new bug budget release, packing their titles with all sorts of "... was I supposed to find this?!" revelations and shareable imagery.
To be fair, gaming as a medium is all about world-building, exploration and immersion. Coding teams are as much architects and sculptors as they are number-crunchers and tech whizzes, the result being environments designed with rewarding curiosity in mind.
As gaming and games have gotten bigger, so too have their worlds and teams in tow. Jonathan Blow's The Witness was created with a team of architects on staff, just to ensure every part of its labyrinthine structure made physical, logical sense. All of which isn't to say the humble secret level is a new thing, but this decade's releases have some real humdingers, if you know where to look...