It's the quintessential hub of Madrid, representing Madrid's reputation as an open and cosmopolitan city. It has accumulated symbols over time: the clock that chimes on December 31st, the statue of the Bear and the Strawberry Tree, Kilometer Zero, the neon sign for Tio Pepe, and the statue of Charles III. Originally, back in the 15th century, it was one of the entrances to the wall surrounding Madrid.