Half-Life 2 will go down in history as one of the most influential games of all time, the impact it has on the videogame industry will assuredly be felt for generations to come.

I'm not referring to the innovative first-person storytelling, the realistic characters or the razor-sharp level design. All that stuff pales in comparison to Half-Life 2's greatest accomplishment: the addition of "the citadel" to the videogame lexicon.

The Citadel is the base for the Combine's operations on earth and the main link to their headcrab-infested alien homeworld. Imposing and ever-present, the Citadel is physical manifestation of the Combine's dominance over City 17 and the whole of humanity.

It's also really, really big.

This development, although seemingly minor, set the standard for naming really, really big things in other videogames to come.

Smash hits like World of Warcraft, Mass Effect, and Fallout 3 have all utilized the latest in citadel-naming technologies, and have all received a rating of 90 or higher on Metacritic (the pinnacle of videogame ratings.)

Coincidence? I think not.

Whenever a game developer wants to put a huge structure in their game, they no longer need to go through the boring, antiquated process of coming up with a new or unique name for it.

With the enormous power of "the citadel," they can focus their precious time and energy on things like fetch quests, lesbian alien sex, or exploding corpses - you know, the stuff that gamers really want.

And, while Half-Life 2 certainly popularized the use of "the citadel," can Valve really be credited with such a monumental breakthrough?

With further research and highly skilled journalism (or GiantBomb), I've been able to track the use of "the citadel" far back through the ages.

The first use of "the citadel" prior to Half-Life 2 can be dated to 3 B.F (Before Freeman), or 2001 A.D., with Gol and Maia's Citadel in Jak and Daxter: The Precursor Legacy.

However, "the citadel" can be traced back much farther - all the way back to 1995 with the release of Lords of Midnight: The Citadel and the expansion for Hexen, Deathnights of The Dark Citadel.

1995 was assuredly the year of "the citadel," with two games not only using the word in their games, but in their titles.

Revolutionary, for sure, but the widespread use of "the citadel" couldn't have been a mere coincidence - it had to have come from somewhere.

And come from somewhere it did - a whole decade prior to the release of both games came a game so innovative, so cutting edge that its impact can be felt over 20 years later.

The game was called, appropriately enough, Citadel.

Dubbed as "THE BEST ARCADE ADVENTURE EVER" by its own box art, Citadel starred some kinda hooded dude and took the player through a large castle, a wasteland, and even - a pyramid.

Pretty standard fare for a platform/adventure game on the BBC Micro and Acorn Electron, sure, but where the game really excelled was in its breakthrough use of "the citadel."

And, even though "the citadel" is perhaps the greatest thing to come to video games ever, we can only ride this wave for so long.

So, to help out video game developers name their enormous buildings without riding on the citadel's coattails, I'm going to supply a list of synonyms which still instil the same sense of awe as "the citadel" with twice the innovation:

bastion, castle, fortress, fortification, keep, manor, stronghold, bulwark, parapet, peel, seat, tower, villa, garrison, observatory, station, ward, watch, and my favorite ... catbird seat.

All mean basically the same thing, but if your game company uses just one of these words, it too could be the hot, new "thang" on the block.

And, while we look to the future for new and better names for really big things, we also look back to the past. So here's to you, "the citadel," a milestone in gaming history.