Both maps are a bit different in size themselves, as this video covers comparing the map sizes of all the games; Constantinople is on the smaller side at 0.94 km2 in size, with Paris being a bit ...

According to this comparison video, Constantinople in Revelations is 0.94 km2 in size, while Paris in Unity is 2.40 km2, so we'd expect Mirage to be somewhere between the two.

Assassin's Creed Assassin's Creed Mirage News PS4 PS5 Ubisoft Assassin’s Creed Mirage Map Size Is Comparable To Constantinople From AC Revelations Michael Harradence / June 19, 2023 ...

According to this comparison video, Constantinople in Revelations is 0.94 km2 in size, while Paris in Unity is 2.40 km2, so we'd expect Mirage to be somewhere between the two.