Leave Plaza Mayor on Calle Mayor and then go left on Pasadizo de San Ginés. At the end of the street turn right onto Calle Bordadores and then turn right again onto Calle Arenal. This lively street brimming with shops will take you to Puerta de Sol.
The square is very famous as for 50 years now, when the clock on its oldest building, Casa de Correos, strikes 12 on New Year's Eve, Spaniards eat 12 grapes to usher in the New Year.
Puerta del Sol is also considered "kilometre zero" for the radial network of roads in Spain (a plaque on the ground indicates this). In the square is also found the symbol of the city of Madrid, the Bear and the Tree Strawberry, a sculpture from the second half of the 20th century that represents the heraldic arms of the city. It is situated between Calle Alcalá and Carrera de San Jerónimo. Behind the Bear and Tree Strawberry, high up on a building, can be seen the poster of Tío Pepe, a bottle of wine with a hat and red bolero, one of the most recognizable figures in the world of Spanish advertising.
This visit will take about 30 minutes.
When you finish, if you're hungry, it is typical in Madrid to drink hot chocolate in the afternoon. The most typical place to do this is Chocolatería San Ginés (Pasadizo de San Ginés 11). The historic and delicious chocolate with churros costs 4€.