This large, multi-towered, 11th-century fortress, raised in Christian/Muslim frontier territory by Sancho III of Navarra and then expanded by Sancho Ramírez of Aragón, broods like a crusader castle above broad plains and is one of Aragón's biggest tourist attractions. Spanish-language tours (€1.50) run several times daily, or you can explore with an audio guide or self-guiding leaflet. There's plenty to see, including a Romanesque chapel and crypt, and you can climb to the upper levels of the two main towers.
The castle is a 5km drive or a 2km, one-hour, uphill walk from Loarre village.