Hi! Welcome to Wayfarer and the forum. As you may know already, a lot of things about Niantic games in general and Wayfarer in particular are organized around S2 cells of different levels. This is a system that cuts the world into “squares” of various sizes. They are identified by their levels (the nomenclature is L0, L1, L2…).
The size, shape and surface of a specific cell level will vary a lot depending on where you are so it’s really best to look them up on a case to case basis. More info here if you are interested.
Your main review area in Wayfarer will be composed from nine S2 level 6 cells, the one you are located in and the 8 surrounding ones. That can contain a lot more cities than just Barcelona and will most certainly cross into France, as you will find out as you keep reviewing 
Then there are also secondary review locations that have been mentioned above, they operate under the same kind of principle, which is why I recommend people check how they work prior to setting them so their locations don’t overlap.
All of the above are (thoroughly researched) community observations, but in the same vein it’s quite clear that nominations don’t go into review in the order they are submitted, it’s nor a first-in-first-out, neither a last-in-first-out system. Just because there is a nomination that is recent and close to you doesn’t mean you are going to receive it for review among your first few ones.
I hope this helps understand the structure of what you are seeing in review a little. Please feel free to ask further if you have questions about any of these areas.