Sadly there are no River Island stores in Barcelona, however there are lots of other similar shops such as H&M which sell similar clothing items for about the same price.
There is an easy way to find out where the River Island stores are located around the world. If you go onto the stores website, they have a whole page designated to store locating.
You can either type in where you are and it will list all of the River Island stores around you in order of how close they are. Or you can type in a country or city where you wish to find out if there are any stores there.
River island does however deliver to Barcelona, so if you really want to shop from River Island, again go on the website and chose the clothing you want, and have it sent right to your door.