It owes its name to “Monte Accettorio” (ab acceptandis suffragiis), since here came the centuriae to vote. In the middle of the square is the obelisk of Psammetic II (VI century BC) moved to Rome during the empire of Augustus. 

It was placed in the Campus Martius as a gnomon sundial (granite obelisk). On the main side of the square is the majestic façade of the Palazzo Montecitorio, seat of the Chamber of Deputies since 1871, began in 1650 by Bernini by order of Pope Innocent X and completed by Carlo Fontana in 1694. 

At the beginning of the century the building was extended toward Piazza del Parlamento.