Well, I already warned you. 
The Forgotten City is a narrative-driven time loop adventure in ancient Rome. Discover the ruins of an ancient underground city, travel 2000 years into the past, and unravel the mystery of who destroyed it by cleverly exploiting the power to wind back time. The fate of the city is in your hands.
One of the game that I know roughly how the mechanic work. I already played several of similar game where you can experience the game only once and it will be not the same afterward.
The game is pretty much simple walking simulator where you walk into a city, where there are roughly 20 people lived in it. There is 1 golden rule, where if someone make a sin, everyone will be punished and turned to gold. Your job is to discover who is the person and prevent it from happening. As you speak to all people, you will learn more about their background and how their feeling living in the city. At the same time, you already will be given several side quest that will help you discover the true ending.
The game is part from perfect, despite high rating. While people praising from narrative perspective, i think the game really shoot themselves on the foot by giving player so many shortcut once you reach certain checkpoint. Rarely you need to involve with 1 npc, once you completed their side quest. Every key, money, items, will be carry forward making you easily able to access locked door once you have it. Being a walking simulator most of the game, a sudden small combat part really turned me off.
Excellent game, especially it was made by 3 core developer. Im more awe with the location storytelling than whole gameplay aspect itself. Definitely a game that you need to get immersed.