Caldas de Montbui

Caldas de Montbui in the Vallès Oriental comarca of Catalonia, just 35 kilometres north of Barcelona, is one of the oldest continually occupied thermal towns in Iberia, with Roman baths dating to the 2nd century AD still visible beneath the medieval streets. The bicarbonate springs here emerge at a constant 74°C — one of the hottest natural springs in Catalonia — and have been used without interruption since the Romans established the settlement of Aquae Calidae. The Plaça de la Font, the town's main square, is centred on an ancient spring where water boils visibly in an open basin, a remarkable survival of Roman thermal urbanism. Modern spa facilities alongside ancient Roman ruins make Caldas de Montbui one of Catalonia's most historically layered thermal destinations.