The tower of the monkey is a medieval tower that originally belonged to the Frangipane family. In the XVI century, its property went to the Scapucci, a noble Roman family that included the tower in a larger building that still exists today: palazzo Scapucci.
The name tower of the monkey comes from an old legend, that explains why on the top of it there is a shrine of the Virgin with a lamp, which is turned on every night. The legend is narrated by the novelist Nathaniel Hawthorne in his notebooks from France and Italy, in 1858:
Mr. Thompson took me into the Via dei Portoghesi, and showed me an old palace, above which rose -not a very customary feature of the architecture of Rome- a tall, battlemented tower. At one angle of the tower we saw a shrine of the Virgin, with a lamp, and all the appendages of those numerous shrines which we see at the street-corners, and in hundreds of places about the city.
Three or four centuries ago, this palace was inhabited by a nobleman who had an only son and a large pet monkey, and one day the monkey caught the infant up and clambered to this lofty turret, and sat there with him in his arms grinning and chattering like the Devil himself.
The father was in despair, but was afraid to pursue the monkey lest he should fling down the child from the height of the tower and make his escape. At last he vowed that if the boy were safely restored to him he would build a shrine at the summit of the tower, and cause it to be kept as a sacred place forever. By and by the monkey came down and deposited the child on the ground; the father fulfilled his vow, built the shrine, and made it obligatory, on all future possessors of the palace to keep the lamp burning before it.Centuries have passed, the property has changed hands; but still there is the shrine on the giddy top of the tower, far aloft over the street, on the very spot where the monkey sat, and there burns the lamp, in memory of the father's vow. This being the tenure by which the estate is held, the extinguishment of that flame might yet turn the present owner out of the palace.