I recall seeing antiques, coins and military memorabilia being sold in stores around the plaza. Besides being a major hang out area during the evening, the Puerta del sol is the geographical center of Madrid. At night this area is transformed with lights and activity. The Plaza de Espana - Statue of Cervantes with a bronze of Don Quixote and Sancho Panza. As with most cities I visited in Spain, Madrid is virtually littered with Plazas.
Plazas are a place for friends and family to gather.
In Madrid they also provide the landmarks for essential navigation. Plaza de Neptuno - The fountain of Neptune dates from the 1700's. Photographs can be used for personal use only, unless other authorization is given in writing.