Here is the full list of all 40 The Forgotten City achievements. It takes around 12-15 hours to unlock all of the achievements on Windows.
Reach the best ending with the smallest number of loops
Help Galerius romance Equitia
Free the captive and shoot her captor with your gun
Topple 10 peeled statues by kicking others into them
Die from hornet stings
Finish the game without looping through time once
Skip the city tour
Intimidate the creator of The Golden Rule
Allow Fabia to die in the collapsing temple
Lie 10 times
Discover Underworld icons Sisyphus, Tantalus, Ixion and the Belide
Save Fabia's life
Reach Ending 3 of 4
Reach Ending 2 of 4
Reach Ending 1 of 4
Loop through time ten times
Reach Ending 4 of 4
Assemble as many people as possible in the Museum
Talk your way through every possible confrontation
Confront the creator of The Golden Rule
Have Duli released from his cell
Save Ulpius's life
Save Iulia's life
Trigger The Golden Rule by stealing 5 times
Steal 2000 coins after the Golden Rule is broken
Solve Vergil's problem
Find treasure using the golden bow
Find all three missing persons
Enter the upper cistern in an unconventional way
Survive the Palace
Gild your first thing
Dodge 3 boulders
Learn the true identity of the stranger by the river
Discover what lies beneath the city
Enter a villa with a daring leap
Read 10 different grafitti
Pick up the sponge on a stick
Get rejected by Aurelia
Loop through time once
Use Photo Mode