Here is the full list of all 12 SUBARACITY achievements.
Built a city for the first time
Created a block of Lv.15 and above
Unlocked 5 characters
Created a population over 3 million
Over 300 years passed
Unlocked 5 buildings over Lv.10
Unlocked 10 buildings over Lv.10
Made a block of Lv.25 and above
Created a city ranked Eagle Class and above
Unlocked 15 buildings over Lv.10
Unlocked over 15 characters
City reached the highest level, Dragon Class