The most famous central square is the official starting point for Spain's 6 National Roads. It is also the most common meeting point, lined with many notable buildings and shops.
There are several points of interest located in this square, such as the statue of Charles III of Spain, Tío Pepe lighted sign on one of the buildings, and one of the most famous sculptures in Madrid - the sculpture of the Bear and the Strawberry Tree - which is also the symbol of the city and is to be found depicted in various ways all around the city.
Wikipedia https://en.wikipedia.org/wiki/Puerta_del_Sol
Info http://www.spain.info/en/que-quieres/arte/monumentos/madrid/puerta_del_sol.html
Address Plaza de la Puerta del Sol, s/n, 28013 Madrid, Spain
Coordinates 40°25'1.313" N -3°42'12.344" E