The streets between the seafront and the railway line are a free outdoor museum of Belle Époque and Art Deco seaside architecture. The villas were built between roughly 1880 and the 1930s by wealthy Parisians, Nantais, and Anglo-Saxons who took the train down for the summer.
Walk the Avenue des Pétrels, Avenue de la Vendée, and Avenue de Concarneau for the best concentration. Look for the slate roofs with elaborate cresting, the polychrome brickwork, the half-timbered Norman pastiches, and the wrought-iron balconies. The tourist office sells a self-guided walking map.