The Najerilla flows from the mountains of the Sierra de la Demanda to the River Ebro in the western part of the province of La Rioja in northern Spain. Here fieldwork and excavations from 2000-2003 examined the varied landscapes of the valley and focused on the excavation of two Iron Age hilltop settlements, Castillo Antiguo and Cerro Molino. The work on Cerro Molino was the most extensive and exposed close-spaced buildings of mud-brick and timber belonging to the Celtiberian period (fourth-second centuries BC), but both hilltops were occupied in earlier periods from the seventh to the fifth centuries. Full reports are given of the structures, material culture and economy of the settlements together with accounts of extensive field-walking undertaken in the vicinity. The report concludes with a wide-ranging overview of the archaeology and history of this hitherto little known area.