noclip.website -- Must See Game Level Site!
noclip is a newly published website that enables you to explore reverse engineered game levels. Many of the games are from Nintendo... who aren't exactly... friendly to YouTube nor modders, so be sure to check it out as soon as possible! You can fly around the game levels using WASD keys, enabling you to easily see behind the scenes about how the game was designed, as well as navigate through all of the textures that made up the level. If you've ever been interested in level design, this is a must see... especially before the lawyers get involved. The entire site is also open source, available on GitHub under the MIT license. Warning though, it's a massive time drain!
Links
http://noclip.website
https://github.com/magcius/noclip.website
Channels recommended in video:
https://www.youtube.com/user/PencakeAndWuffle/videos
https://www.youtube.com/channel/UC0fDG3byEcMtbOqPMymDNbw