How big is Vein?

Like, it has to be large enough to have EVERY map, so like.. 2 cities? Or 3?? Like, the main city of Vein where our Church is located, the city of falling flames and Eva’s sand city. Plus a huge snowy mountain and effectively a dried out sea?? It’s either super large and Silvia’s must covers EVERYTHING, or somehow not as large as the maps suggest, and somehow nobody ever found a way out