The use of blue and white "Azulejos" tiles to decorate the interior and exteriors of public and private buildings in Porto has been popular since the invasion of Spain and Portugal by the Moors of North Africa in the 711 A.D. When the armies of the Moors were driven out by the Christian kings many of the craftsmen stay behind and continued to make tiles. The style changed from using coloured tiles to make concentric patterns, to tiles that showed pictures.Over 20,000 "Azulejos" tiles have been used to decorate the interior of Esação de São Bento Railway Station in Porto. They were laid between 1905 in 1916. The major benefit of using tiles on walls rather than painting them is that they do not need repainting every 5 years. They are also cool to the touch and help to keep the temperature down on hot summers days in the railway station ticket hall.