The best feature of this airport is unquestionably the two large outdoor terraces located on each side of the main building. There is a Haagen-Dazs in the southern terrace and a Costa Coffee in the northern terrace. Very few airports have open air areas these days, most were closed due to security concerns by the turn of the century. My all-time favorite remains Bangkok Airways' Koh Samui airport where the entire airport is open-air with a collection of thatch roofs without walls. Makes you want to change into your swimsuit and look for the pool!
Back to Barcelona, the other area that is big and bright in Terminal 1 is the shopping area. The stores are much larger than usually found in airports. The Desigual shop, a brand from Barcelona, is larger than I have seen in most shopping centers. There are over 30 restaurants, bars and coffee shops with a great choice of local flavors to be found beside the usual fast-food brands.
If your destination is Barcelona, you will get to town quickly being that the airport is only 14km (9 miles) from city center. After sightseeing the best known attractions, the Sagrada Familia, Park Guell, Casa Batllo, etc., look further afield and discover Barcelona's two cable cars and three mountain trains! You will get great views of the city from any of these.
Last but not least, the food! This is Catalunya country with mountains and the Mediterranean coast. The cuisine draws from both sides with the fantastic seafood along so many fresh vegetables to choose from. Do try at least a few of Barcelona's restaurants, but do not miss a visit, including lunch, at La Boqueria Food Market.