Civilizations are built in layers. Any town more than a hundred years old will have layers - buildings, customs, and infrastructure of different eras.
Plaques! Another example of world building in layers. If your characters have a sense of history, so will your readers.
Statues. Plaques. Shrines. Cemeteries. Buildings of different eras. Old structures that have been repurposed. All of these will give your city the feeling of life, of a past - and that will be reflected in your characters.
A common practice in pre-industrial societies is to use cut stone from other structures. There are Byzantine and Nabatean stones in the walls of "old quarters" throughout the Middle East.
In London, you can walk past at least one Victorian structure built over an ancient Roman bath
And of course, the excavation of Troy at Hisarlik, in Turkey, revealed the ruins of SEVEN complete cities, built one on top of another.
Layer example 1: In LOTR, the characters live in and travel through dozens of places that are relics of those who came long before: Moria, Weathertop, the Argonath. These convey a sense that Middle Earth is a place with its own history - one that would exist even if the reader wasn't reading about it.
My own novel, "The Wrong Sword," takes place in medieval France. The castles are new, but there also Roman roads and ruins already more than 1,000 years old.
Give your world history.