Colossal Order published its 14th City Corner dev diary on October 29, 2026, this time focused on the environmental work behind the upcoming Park Adventures expansion for Cities: Skylines II. Instead of a single developer, the studio brought in both an artist and a programmer to walk through how terrain, vegetation and biomes get built and tuned.
The headline addition is four new biomes: arid, tropical, alpine and Mediterranean. According to the team, the vanilla maps felt visually flat, so they went back into the existing climate and biome code to build something more distinct for each environment. A biome is not just a label slapped on a map at the start of a new game. It actively changes what grows and what kind of rocks show up around your city, with arid zones getting cacti and red-toned stone instead of the grey rock and trees you would find in colder regions.
Players can still override this manually and plant whatever vegetation they like regardless of biome, but the natural spawn behavior follows the new rules. Getting the look right took more than swapping assets per biome. Colossal Order says ground textures like grass, dirt and sand had to be reworked so transitions between them blend properly, since mismatched textures made landscapes look patchy even when each texture looked fine on its own.
Trees Got a Visual and Performance Pass
The diary also covers tree rendering. Cities: Skylines II uses photographic LODs for trees rather than simplified 3D models at a distance, and the team has been refining those representations so forests and parks hold up better when you zoom out. New trees, including bamboo, are also sharing textures across different growth stages instead of needing a separate texture per stage, a change aimed at keeping performance in check as more vegetation gets added.
What This Means for Modders
The new maps themselves are tied to the paid Park Adventures expansion, but Colossal Order confirmed the four new biomes will be free for everyone through the Editor once the accompanying update lands. That is good news if you build or download custom maps, since it widens the toolbox without requiring the DLC.
If you run vegetation or terrain mods, keep an eye on how they interact with the new biome-driven spawning once the update is live. Back up your save files and any custom map projects before updating, and expect some older terrain or tree mods to need adjustments if they touch the same texture or LOD systems Colossal Order has been reworking.
Source: Steam · Image: Steam
