Early plans for Half-Life 2 sound wild, including visits to cities like Chicago and LA, several Combine bases, and a sequence where a plane crashed into a skyrise that was cut after 9/11

Thanks to Half-Life 2: Raising the Bar and the Half-Life 2 beta leak from 2003, we've had a few little looks at concepts Valve considered for the FPS sequel but had to cut during development. For instance, thanks to files found in the leaked version, we know there were plans for a level set on an icebreaker ship that would lead to a mini-submarine trip to an underwater base—an idea that ended up being re-used in the Half-Life 2: Episode 3 synopsis, and the fan game based on it.

The recent 20th anniversary documentary has shone even more light on the earliest plans for Half-Life 2. Interestingly, those early plans weren't doing much to build on the plot of the first game. "The first two years we tried a lot of things," says writer Marc Laidlaw, "and a lot of those story arcs that we had initially didn't have really any carryover from Black Mesa or any of that."

Those ideas included an Earth that was suffering under multiple invasions from different alien species. One bug-like alien species survived in the form of the antlions, though there were originally much bigger plans for them. "It had three alien races," engineer David Speyrer says of the initial Half-Life 2 concept. "The Warrior Aliens, the Insect Aliens, and the Spy Aliens. And it had a Prague-like city, which ended up being the closest thing to City 17."

While City 17 draws inspiration from real-world cities like Prague, Sofia, and Paris, a vignette published in Half-Life 2: Raising the Bar mentions that it's a lot like City 40 and City 49, and presumably every other world city under alien control, which would make visiting them a bit redundant. Presumably that wasn't true of the world tour that formed one abandoned concept for Half-Life 2.

"I remember we were really ambitious at the beginning," says level designer David Riller. "I remember we designed, what, four cities at one point? Prague, Jerusalem, Chicago, Los Angeles, I believe. We had an Arctic base, an underwater base, an icebreaker ship, an airplane sequence that crashed into a high rise, which we cut right after 9/11. We had several Combine bases in the Wasteland, we had the Air Exchange, which is where they were taking the atmosphere from Earth, we had a train depot, and so on."

Speyrer lays the blame for this sprawling scale to "sophomore anxiety," a desire to top what Half-Life had done before that resulted in some impractical ideas. Later in the documentary it's mentioned that after a research trip to a real-world icebreaker ship they realized how difficult it would be to make combat fun in such tight spaces, which is why it was scrapped.

Laidlaw explains that a lot of these early, throw-it-all-at-the-wall concepts were abandoned because, as he puts it, "Gabe kept asking, how is this Half-Life?" Laidlaw suggests that it was only when the team decided to bring back characters like the first game's scientists, tying the sequel directly to Half-Life, did it solidify into Half-Life 2's final form.

"We really obviously had to scale back what we were trying to do," says Riller. "But that's OK, to go a little bit nuts at the beginning."