Based on Daggerfalls scale, I'd estimate that City Isle (the name of the island) would have the surface area approximately the size of Wales (approx. 20,000km^2). The size of the city itself would vary wildly based on which map you use as a source. If you say the imperial city is 10% the size of City Isle it would be equivalent to Tokyo City (2,200km^2). The greatest ancient civilization and the closest analogue would be Rome which is about 1,200km^2 (not sure how it compares to the surface area of ancient Rome).



The city in the picture, if scaled to the size of the island, looks to be around 50% of the surface area of the island, so about 10,000km^2. Five Tokyo cities...



That's the thing about Elder Scrolls lore, if you start to pick it apart, it gets really f**ky really fast.