I was having a discussion about Halo campaigns and the subject of unique environments came up and about which game felt more "same-y" or had the most varied locales. While I didn't get around to it at the time, I decided to go do an inventory of all the unique environments in each of the main Halo games' campaigns (ODST isn't counted as it takes place mostly in a single city, with many levels overlapping in the same locales). The environments and levels are not distributed evenly, with some environments being split across multiple levels, either due to backtracking or because you have smaller levels in the same environment that can be combined to form a single "super-level," both of which have the effect of reducing the number of unique environments. However, some levels have more than one unique environment, which of course increases the number of unique environments but also has the effect of making those unique environments rather small in scale as they're having to share a single standard-sized Halo level. It's also worth pointing out that having a mix of indoors and outdoors areas is common in Halo, so I wouldn't necessarily count an indoors area contiguous with the outdoors area (or vice versa) as a unique environment. Also not counted is when a stage visually changes in overall look despite not really shifting locales (e.g., The Covenant in Halo 3 shifting from a forested area to a barren snowy area when you pass through the cave to get to the double Scarab battle).

Halo 1 has seven distinct environments: The PoA, Chief's initial LZ area (beam emitter region), the T&R, the SC island, the control room region, the Flood containment facility & surrounding swamps, the Library. If you count the plateau the T&R is parked over as separate from the T&R itself, that raises the total to 8. In any case, you continue to run into unique environments every level up to The Library, but for the remaining three levels you are revisiting locations you've already been to, thus making them "remixed" version of those prior levels.

Halo 2 also has seven distinct environments: Cairo Station, Mombasa, the gas mine, Delta Halo temple ruins, Delta Halo quarantine zone/Library region, Delta Halo control room region, High Charity. Cairo Station is the only one containing a single level. The remaining six environments are split across two levels each.

Halo 3 has eight distinct environments: jungles/dam area, Crow's Nest, Tsavo Highway, Voi, Ark cartographer building region, Ark control room region, High Charity, Alpha Halo v2 control room area. Voi is the only one split across two levels, with Floodgate being the Two Betrayals to The Storm's AotCR.

Reach has eleven distinct environments: Visegrad, Sword Base area, Viery Territory part 1 (night), Viery Territory part 2 (day), Sabre launch facility, in orbit around Reach, the Ardent Prayer, New Alexandria lower levels, New Alexandria skyscraper tops, underground ice cave, Aszod ship-breaking yards. Nightfall and Tip of the Spear technically take place in the same environment (the Szurdok Ridge), but the difference in time of day, scale, and topography, and the fact that neither of them share any geometry, serve to make them distinct from each other. Long Night of Solace is the first level to have multiple environments, taking place at the Sabre launch facility before quickly sending the player to low orbit for a space battle, and finally sending them aboard the Ardent Prayer, the only Covenant environment in the game's Campaign. Taking place in a single level makes the time spent in each locale rather short. The Package also is split across two unique environments, but the first of those is simply a remodeled ONI Sword Base; the underground ice cave where Halsey is studying the buried Forerunner structure is essentially just a Firefight map. So, Reach technically has the widest variety of environments, but many of them share the same level, making your visits to them rather brief.

Halo 4 has nine distinct environments: the FUD, the Chief's initial LZ area, Requiem's core, Requiem's jungles, Infinity's crash site & interior, Requiem canyon area, floating shield tower structures, Ivanoff Station, Mantle's Approach. The level Infinity is one of those levels that has the environments spread across multiple environments, with the jungles and the Infinity not being contiguous with each other and distinct enough visually to possibly count as separate environments. If you count the whole level as just one environment with an outdoors and indoors part, though, that drops Halo 4 to eight environments.

Halo 5 has eight distinct environments: Kamchatka, Argent Moon, Meridian, Swords of Sanghelios base region, Sunaion, Genesis part 1 (Blue Team & Osiris arrival area), Gateway to the Domain, Genesis part 2 (snowy area). Like Halo 2, Halo 5 makes heavy use of splitting single environments across multiple levels, including three instances of non-gameplay levels where you interact with friendly NPCs. Still, Halo 5 manages to have just as many distinct environments as Halo 3 did, and more than Halo 1 & 2.

So, in summary, aside from Reach, which crammed multiple environments into not just one but two levels (one of which was itself a partial retread of a previous level), Halo games have historically managed 7 or 8 truly unique environments.

So, which game do you think had the most varied environments? What do you think constitutes a unique environment? Discuss.