You have reached the third part of the Gran Vía which connects Plaza del Callao to Plaza de España. This stretch of road was completed in 1929 after four years of construction work.
Callao, the name of the pedestrian square, is a reference to the Peruvian port where a fierce naval battle took place during the Spanish-American War. Today it is the epicenter of shopping in Madrid: among the various buildings, the art-deco style façade of the historical "Cines Callao" building merits your attention.
Before you go down to Plaza de España, note the original shape of number 46, which is the Press Building that was built in North American style on behalf of the Association of Journalists. Even today on the upper floors above the four movie theaters, you can find offices of political parties, newspapers, and publishers.
At the beginning of the descent you'll first see the curvy façade of the Carrión Building, called the "Capitol Building" thanks to the movie theater at the bottom. As you can see, its aerodynamic shape resembles the prow of a ship. Later, just a little bit before the "Santo Domingo" metro stop, you'll come across a pair of theaters facing each other: they are the Rialto and the Lope de Vega. The latter, along with the hotel that precedes it, date back to the late forties.
Before reaching Plaza de España look at number 78, which is a building with theater connections called the Coliseum Building: it was commissioned by the composer Jacinto Guerrero, who also lived there. Another famous tenant was Concha Piquer, a famous singer of traditional Spanish music.
And now if you'd like to take a break from your walk, I recommend going into the hotel next to the Coliseum Building and enjoying a refreshing drink at the lounge bar on the fourteenth floor, where you can also enjoy a splendid view of Plaza de España.
FUN FACT: look at the top of the building at number 60, where you'll find a naked and mysterious bronze statue called "The Roman" who looks like he's ready to throw that temple he's holding at someone down below!