The Red Tower Monument · Caldes de Montbui, Vallès Oriental, Barcelona La Torre Roja rises near the top of the hill that bears its name, on the border between Caldes de Montbui and Sentmenat, and shares its plateau with the remains of a 5th-century BC Iberian settlement. The site, formerly called Puig Castellar, was Iberian and later Roman, and remained occupied in the Middle Ages. The fortification consists of two concentric towers: an outer one, 10.5 meters in diameter, and an inner circular one that projects 1.40 meters above the first and may date from around the 10th century; both preserve courses of opus spicatum, and the inner one retains traces of exterior plaster. There is no agreement on its origin: some believe the inner tower was added inside an earlier Roman tower, others that it was the other way around. The base, with regular ashlar blocks, recalls Roman constructions. Photo: Carlos Pino Andújar (CC BY-SA 3.0) What to see and do in Caldes de Montbui