Right at the center of the square between the two fountains, you can see the recent statue of Charles III of Bourbon on horseback. Follow his example and direct your gaze toward the red brick building in front of you. This is Casa de Correos dating back to the second half of the 1700s, and currently the seat of the Presidency of the Region of Madrid. If you're in Madrid at the end of the year, be sure to celebrate New Year's in front of this building! In fact, on the night of the 31st hundreds of thousands of people gather here to perform the grape ritual: you have to eat a grape for each of the twelve chimes of the clock built into the central tower.
And speaking of Madrid traditions: to the left near the corner of Calle Alcalá, you can see a group of statues in bronze and stone depicting a climbing bear and a strawberry tree. It's the famous "Oso y Madroño" statue, and the symbol of Madrid that you'll find on every postcard.
Now head towards "Casa de Correos" and you'll walk through an area full of history. It was here that the 19th century revolt against the French began and was immediately stamped out the next day with the shootings that are also dramatically represented in the famous painting by Goya at the Prado. Also here, the President of the Government was assassinated in 1912, the First Republic was proclaimed in 1931, and a few years ago the so-called "Indignados" camped out here led by the leader of the "Podemos" party, Pablo Iglesias.
Now look down at the sidewalk near the exit of the subway station and try to find a plaque indicating Madrid's kilometer zero. This is the exact geographical point from which the kilometers of the six main "Carreteras", or Spanish highways, that depart from the capital begin their counting.
Continue on this side and go past the entrance of Casa de Correos, heading towards the famous Calle Mayor in front of you: this road crosses all of ancient Madrid.
FUN FACT: do you know why this square is called Puerta del Sol? In the sixteenth century, many comuneros, or poor and hungry people, entered the city from this side. To stop them, a type of fortress was built with a large sun facing east painted on it, just like the sunrise.