The Puerta del Sol is the centre of the Spanish road network, known as 'Kilometre 0'. It translates to 'Sun Gate' and is one of the most famous and liveliest areas in the city of Madrid. This square features many attractions, of which the Puerta del Sol Clock is especially notable. This clock marks the tradition of eating 12 grapes, established in 1909, with a bell chime. This tradition involves eating a grape for each bell strike on December 31 at midnight. This celebration was first aired live in 1962, and has become an annual event since. It is believed that eating grapes at midnight will ensure prosperity in the new year.

Puerta del Sol was initially a city gate in the wall, encircling Madrid in the 1400s. Suburbs began to form outside the wall. The gate was decorated with a rising sun, which is how it received its name. The gate was turned to the east. This gate was a popular meeting place until the 19th Century. Famous French architect Maquet developed a project for construction of a post office on this site, which was completed in 1766. This building hosted the Ministry of Interior during the totalitarian regime of Franco. Today it is the seat of the Madrid Community Presidency. The municipal government, a different governing body, is housed at another site. Many of the Puerta's attractions are considered symbols of Spain, both at home and abroad. There is a remarkable statue of King Charles III on the south side of the square. He is often referred to as the mayor of Madrid, because he implemented an extensive public works programme. There is a sculpture of a madrono tree in the northern part of the square, as well as a statue of a bear. The madrono is a symbol of Madrid. This tree is part of the Ericaceae family, endemic to the geographical regions of North America, western Europe and the Mediterranean. These evergreens can grow to as much as 25 metres. The fruit is a reddish berry with a slight resemblance to strawberries, which is why the madronos are called Strawberry Trees in Western Europe.

The Calle de Arenal and Calle Mayor are located in the western part of the square, and the well-known 'Tio Pepe' sign situated above the building between them. In the past there was a fountain at the square, which has since been replaced by the Venus or Mariblanca. The 'Kilometre 0' mark is to the north of the former Post Office building. It represents the core of Spain. It forms the basis of the Spanish road network and is often the site of protests and rallies due to its symbolic significance. Protests against wars and terrorist attacks were often organised here in the past, like the one related to the Madrid train bombing. Additionally, Spaniards protested against ETA terrorism and the government's involvement in the Iraq War.

There is a subway station called Sol beneath the Puerta. The square is bordered by Parliament, Palacio Real, Plaza Mayor and Atocha railway station. Palacio Real is the residence of the Spanish royal family. It frequently hosts official ceremonies and events. The king and his family do not actually live here - they reside at the Palacio de la Zarzuela outside Madrid. In the 10th Century there was a fortress where Palacio Real stands today. In the 16th Century the fortress grounds were replaced by the Old Castle or Antiguo Alcazar. It burned to the ground in 1734. King Philip V commissioned construction of a new palace on this site. The Palacio Real is the biggest palace in Western Europe, covering an area of 135,000m². A stroll through the Puerta may end at the palace, located right to the south-west of the square.