(b. 1668, Roma, d. 1729, Roma)
As an architect, he was influenced by Francesco Borromini. His first major work was the design of the Baroque Porto di Ripetta, the port of Rome, on the banks of the River Tevere or Tiber. With the design of this port Specchi broke with the classicising architecture of his teacher Fontana. The port was destroyed in 1874 with the development of flood defences and the river bank road of Lungotevere, and replaced by Rome's Ponte Cavour, and his fountain at the top of the port was moved to a nearby site.
As the papal architect, he submitted a design for the famous Spanish Steps leading up from the Piazza di Spagna to the French church of the Trinitŕ dei Monti, but the proposal by the little-known Italian architect Francesco de Sanctis was preferred by the French monks and the Steps were constructed to his design between 1723 and 1728.
He designed and was involved with alterations to various Roman palaces: he designed the Palazzo de Carolis on the Via del Corso (now the headquarters of the Banco di Roma), the high altar in the Pantheon, the Palazzo Pichini; and made alterations to the Palazzo Verospi and the Palazzo Albani, and additions to the Palazzo del Quirinale.
In 1711 he became a member of the Academy of St. Luke, the artists' academy in Rome.