Calle Serrano in Madrid (€11,400/m2), Paseo de Gracia in Barcelona (€9,915/m2) and the main streets in the centre of San Sebastian, such as Avenida de la Libertad, Calle Hernani or Plaza de Guipúzcoa (€8,040/m2) are some of the most expensive in Spain to buy a house, according to a report by Tecnita