The document describes several castles located in Catalonia, Spain. It provides brief descriptions of the Miravet Castle located on the River Ebro near its mouth in a small town. It also mentions the Tower of Sant Joan in Amposta, a municipality on the River Ebro with a population of around 20,000. Additionally, it lists several other coastal and inland castles and towns in the Tarragona province, including Altafulla, Tamarit, Amposta, Calafell, Vilafortuny, Les Piles, Biure, and Riudabella, providing their locations and populations ranging from around 1,000 to 30,000 inhabitants.