Here is the full list of all 10 Poly Towns achievements.
Accumulate 1,000,000 coins.
Accumulate 500,000 coins.
Build your first town hall.
Accumulate 100,000 coins.
Accumulate 50,000 coins.
Have 1000 villagers.
Have 500 villagers.
Have 250 villagers.
Have 100 villagers.
Accumulate 10,000 coins.