Puerta del Sol has not only been Madrid’s center since the 15th century but also Kilometer Zero for all of Spain’s roads. Because the “Gate of the Sun” is surrounded by city landmarks and entertainment plus is a major underground transportation hub, the square seems busy 24/7. This provides lots of eyeballs to view the giant Calvin Klien billboards. The neon sign for Tío Pepe – a brand of sherry owned by the González Byass – has been a square landmark since 1936. On the right is an equestrian statue of Charles III. He was the King of Spain from 1759 until 1788.