With the Cities: Skylines popping up after the reveal.
management game, the achievements list should help shed some light on what we can expect from the sequel.

Cities: Skylines 2 achievements
We haven't listed all Cities: Skylines 2 achievements here, as many are standard fare like 'build every building in the game' or 'reach 100,000 citizens,' so we've instead put down the ones we feel are the most notable.
- The size of golf balls: experience a hailstorm
- Out for a spin: experience a tornado
- Now they're all ash trees: experience a forest fire
- Everything the light touches: unlock 150 map tiles in a single city (the first Cities: Skylines maxes at 81)
- Things are not looking up: experience a rat infestation
- Spiderwebbing: have 50 active transport lines
As mentioned there are plenty more achievements (via True Achievements), but these are the ones that we think present the newest and unique scenarios and additions to Cities: Skylines 2.
If you want even more from the city-builder ahead of its release later this year, we've got a list of the management games, if you want to dive into the genres ahead of Cities: Skylines 2.