If you visit Madrid, Plaza de Cibeles (metro: Banco de Espana) should be a stop on your itinerary. It is by far the prettiest and most interesting intersection I found in Madrid. It is located at the intersection of Calle de Alcala, Paseo del Prado, and Paseo de Recoletos. There, you will see the Fountain of Cibeles, with a statue of the goddess Ceres (aka Cibele) being pulled in a chariot by two lions.
You'll also see the magnificent Cibeles Palace (aka the Communications Palace)-and if you love architecture, you'll want to study this one awhile from several different angles. Formerly the site of the headquarters of the postal service, it is now city hall. But truly, it looks like it should be a royal palace, not a government office building.
Continue on down Calle de Alcala and you will come to one of the entrances of Retiro Park. Walk north from the Plaza along Paseo de Recoletos for a lovely walk beneath the trees among outdoor fountains. When I was there, there was an outdoor art display set up along the paseo, which was really cool.
Or head south from the Plaza on Paseo del Prado past the Naval Museum and the Madrid Stock Exchange to the Prado Museum.
If the Real Madrid football team wins a championship, Plaza de Cibeles is where fans flock to celebrate. Plaza de Cibeles is an excellent intersection for people-watching. The plus for me is that it’s a wide open space, not crowded in on all sides by buildings, making it far less claustrophobic than some plazas in Madrid. With so many interesting streets branching off from it, and so many beautiful sites on the plaza or close by, it’s my pick for prettiest plaza in Madrid.