If you're not familiar with Noclip (the website, not the documentaries), I have a treat for you. Coded and maintained by creator "Jasper", Noclip.website contains versions of game levels that you can fly around in 3D to take a closer peek at. The site features a heck of a lot of Nintendo games (and some Dark Souls), but Jasper has also shared a bit of toying with Half-Life 2's levels. They've recently stitched together (almost) all of HL2's levels to do a bit of a flythrough showing off how they look all lined up in space together. Surprisingly decent, it turns out.
On the Noclip website, you're only able to load one of the game's levels at a time. Jasper decided to cram all of them together though. Here's their quick video flythough (which deserves for the sound to be on), heading through several sections in the interior of levels before flying up to check out the full game map as it's connected together.
i loaded all the half life 2 maps at the same time pic.twitter.com/d1dsaMIceW— Jasper (@JasperRLZ) July 10, 2021
Jasper explains further down in the replies to their Tweet that they skipped loading two of HL2's levels that didn't play particularly nice with the code they'd written to connect each level together. All the rest look pretty neat all lined up though.
You might have expected for HL2's levels to double back on one another pretty often when all hooked up like this. Since they're separated into different levels, they don't need to be able to share space with one another coherently—and yet they pretty much do!
Jasper often shares neat visual effects tech based on things found while getting various games working for Noclip. They've continued sharing some other interesting facts about HL2 as well, including how water reflections work and some neat environment building tricks.
If you've never played around on Noclip, I recommend doing so. You can also fly about in the Portal games and Team Fortress 2 maps if that's your jam. Or an absolute ton of Nintendo games.