The building known as Palazzo dei Conservatori, seat of an elected magistrature which had the task of administering the city, goes back to the middle of the 15th century.
The building originally featured a portico on the ground floor and Guelf-cross windows on the first floor, in addition to a row of small windows on the mezzanine floor. Michelangelo re-designed the facade, adding gigantic Corinthian pilaster strips on high pedestals, flanked by pillars in the portico on the ground floor.
As in the case of Palazzo Senatorio, the building was crowned with a balustrade and statues. The transformation of the building also affected its interior configuration, as a result of alterations to the windows on the first floor.
The central one was eventually created by Giacomo della Porta and is much larger than the others, making an exception to Michelangelo's plan.