You will enter every city in Expeditions: Rome, but most of these won't be visible. There will be a strange fog covering most of them. By scrolling through, you will see that the only way for the player to remove this fog is to walk through it.
It is impossible to scout the area in advance, so every city will start with a fog. For the fog to be removed, players must go to every corner of the map.
Related: All riddles and answers in the Olympion quest in Expeditions: Rome
Sometimes, in Expeditions: Rome, random events will occur that do not require the player to act in any way. This is because the events are hidden behind the fog, so you must make sure your allies are fully healed before traveling from city to city for the first time.
For example, Bastia will be injured during the Olympion quest without warning when entering the temple of Apollon. If he is already injured, he will suffer an even greater injury. There is no time limit for any task in the game, so it may seem like it will take a while, but healing companions is worth the wait.
For more information on Expeditions: Rome, check out What Commanders should I pick in Expeditions: Rome? and Can you save Gaius Julius Caesar in Expeditions: Rome? on Pro Game Guides.