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Half-Life 2's Citadel is 3 times taller than everyone thought, says guy who spent 9 years thinking about it

Half-Life 2
(Image credit: Valve)

When visiting City 17, don't forget to check out the Citadel. You can't miss it: it's a massive black alien structure in the center of the city, looming over the remnants of the human race with Dr. Breen's cozy office occupying the top floor. Half-Life 2 begins at the foot of the Citadel and ends on its roof, with a slight detour to everywhere else in between.

The Citadel is a tall building. It's so tall you can see it pointing to the heavens with its tip buried in the clouds even hours after you've left the city itself.  But how tall is it, exactly? Half-Life fans wanted to know.

In 2009 someone emailed Half-Life 2 writer Marc Laidlaw to ask how tall the Citadel was.

Laidlaw, apparently, didn't know either. According to the person who emailed him, Laidlaw asked a Half-Life 2 artist, and that artist said it was 'at least a mile' high, adding: "If you can find someone with a HL2 tree, they could load it up in model viewer and multiply the size by 16 (because this is a skybox version) you’ll get an exact height."

Various calculations ensued, and in 2012 it was ultimately determined that the Citadel is 2,569 meters (8,430 feet) high. That's a little over a mile-and-a-half. Extremely tall! (Note: initial calculations showed it being even taller, nearly 3,000 meters, but those calculations were revised to account for part of the structure being underground.) Here's an image created for scale alongside other buildings on Earth. And these days, even the Combine Overwiki accepts this height as correct.

(Image credit: Valve)

But a redditor named Rscreamroad didn't quite buy it, and it's apparently bothered him for the past 9 years or so, ever since the Citadel's height was calculated. He decided to do some re-calculating, and posted an extensive account of his findings on Reddit. 

"Over the course of these 9 years, I had a lot of objections that destroyed my immersion in the game," Rscreamroad says in the post. "I want to at least try to deliver my ideas to the community and resume this discussion."

Part of Rscreamroad's issue is that if the height of 2,569 meters is correct, that would mean the Citadel is only about 250 meters wide, which doesn't make a lot of sense for those who have been inside the Citadel. We've seen not just how tall the building is but how thicc it is, having taken an extensive Combine pod ride through its interior near the end of Half-Life 2. 250 meters (820 feet) doesn't seem quite big enough to hold everything we've seen in there, from fleets of gunships to striders stomping angrily around inside. The track the pod rides on is quite long and implies an interior width considerably bigger than 250 meters.

So, Rscreamroad did some investigating. He loaded the level that takes place at the top of the Citadel and looked down at the texture of the city below, which he eventually assumed was based on a real satellite image. In the game files, that cityscape was actually four different images, and after pasting the images together, Rscreamroad compared it to real cities, eventually discovering that the view of City 17 from the top of the Citadel was actually created from a picture looking down on New York City. And the camera position for that picture is a height of 8,773 meters. When you're at the top of the Citadel looking down, the city is nearly 9,000 meters below you.

Basing the height of the Citadel on an image of the ground below might not be the most scientific conclusion, considering the artists probably just picked an image that looked good and would give the players an impression of being very high in the air. But when Rscreamroad loaded the Citadel model from Half-Life 2 into Blender, he found that it wasn't really that far off. His measurements in Blender concluded that the Citadel is "27,580 feet or 8,406 meters. It was also 860 meters wide and went 230 meters underground."

Rscreamroad's image of the Citadel's height, posted on Reddit (Image credit: Rscreamroad on Reddit)

If Rscreamroad is correct, that's considerably taller than the height of 2,569 meters. It's over five miles high. It makes the Citadel about three times as tall as everyone has assumed for the past decade. And being that tall makes the interior wide enough that the long Combine pod ride makes much more sense.

Rscreamroad isn't entirely sold on this new measurement himself, however. He says: "The truth is that the Source engine has a bunch of different versions [of the Citadel model]. On the developer resources I found information that they began to use the 1/12 scale for the skybox unit in the latest versions of the engine. And in some cases, 1 unit is not equal to 1 inch, but 2/3 inches. And the Blender itself, depending on versions 2.79 and 2.8+, slightly changed the mechanism for converting model sizes relative to loaded models."

I'd say a five-mile-tall Citadel seems... a bit too high, to me anyway. At the very least, it looks like the Half-Life community has something new to argue over. If you'd rather watch a video than read the entire Reddit post , Rscreamroad made a video too and you can watch it here on YouTube.

Christopher Livingston
Chris has a love-hate relationship with survival games and an unhealthy fascination with the inner lives of NPCs. He's also a fan of offbeat simulation games, mods, and ignoring stories in RPGs so he can make up his own.