The red brick building in Puerta del Sol Square 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.