Early plans for Half-Life 2 are wild. They include visits to cities such as Chicago and LA, multiple Combine bases, and even a sequence in which a plane crashes into a skyrise, which was cut after 9/11.

Half-Life 2 Raising the Bar, and the Half-Life 2 Beta leak from 2003 have given us a glimpse of some concepts Valve had in mind for the FPS sequel. However, they were cut during development. Files found in the leaked version reveal that there was a plan for a level that would be set on an icebreaker that would lead to an underwater base via a mini-submarine. This idea ended up being reused in the Half-Life 2 Episode 3 synopsis and the fan-made game based on it.

The recent 20th anniversary documentary sheds more light on the early plans for Half-Life 2 The early plans for Half-Life 2 didn't do much to expand on the plot of the original game. "The first two year we tried a number of things," writes writer Marc Laidlaw. "And a lot those story arcs we had originally didn't really have any carryover from Black Mesa, or anything like that."

These ideas included an Earth under constant invasion by alien species. The antlions were the only bug-like aliens that survived, although there were initially much larger plans for them. Engineer David Speyrer recalls the original Half-Life 2 concept: "It had 3 alien races." The Warrior Alien, the Insect Alien, and the Spy Alien. It had a city that looked like Prague, which was the closest thing to "City 17."

While City 17 is inspired by real-world cities such as Prague, Sofia, or Paris, a vignette in Half-Life 2's Raising the Bar mentions it's similar to City 40 and City 49 and, presumably, every other world city that has been taken over by aliens, making visiting them redundant. Presumably, that wasn't the case with the world tour concept that was abandoned for Half-Life 2.

David Riller, level designer, says: "I remember being really ambitious in the beginning." "I remember designing, what, four city at one point?" Prague, Jerusalem, Chicago, Los Angeles, I believe. We had an Arctic Base, an Underwater Base, an Icebreaker Ship, and an airplane sequence which crashed into a High Rise, which we cut just after 9/11. We had several Combine base in the Wasteland. We also had the Air Exchange where they were removing the atmosphere of Earth.

Speyrer blames this massive scale on "sophomore anxieties," a desire for Half-Life to surpass what it had done before, which led to some impractical concepts. In the documentary, it is mentioned that after visiting a real-world ship with icebreakers they realized it would be difficult to make combat enjoyable in such small spaces.

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 says that the final Half-Life 2 was only achieved when the team decided on bringing back characters from the first game, such as the scientists.

Riller says, "It was obvious that we had to reduce the scope of what we were doing." "But it's okay to go a bit crazy at the start."