Porta del Popolo ,Bernini and the eight-point star symbolism

The monumental gate was erected by Vignola in 1561 and bears the coat of arms of Pope Pius IV. It is said that Vignola worked on an original design by Michelangelo. Gian Lorenzo Bernini designed the six mountains and the star above the coat of arms in 1655  that are part of the decoration of the inner gate. They were designed  to celebrate the arrival of Queen Christina of Sweden. The statues of St. Peter and St. Paul by Francesco Mochi were added in 1658. Behind the gate one of the most spectacular views of Rome, Piazza del Popolo.

Queen Christina of Sweden embraced the Catholic faith and this event led to the belief that other kings or queens might follow her example. For her arrival in Rome in 1655 Alexander VII had Bernini to decorate the inner side of Porta del Popolo. "Felici Faustoque Evento" (to the happy and propitious event) one can read in memory of her entrance.

The heraldic symbols of Pope Alexander VII can also be seen on the dome of the Chigi Chapel in S. Maria del Popolo; the chapel gained a wide fame in recent years because novelist Dan Brown set episodes of his novel Angels and Demons there .

Universal Symbolism
The eight-point star  appears in cultures around the globe. It can be found on national flags and in religious iconography. It carries various meaning associated with each culture that utilizes it. Eight is an important number in terms of realizing balance, and although it isn’t always illustrated by a star, it appears in the eight-paths in the way of Buddah and eight immortals in Chinesse tradition. Its universal symbolism is one of balance, harmony, and cosmic order. Its pattern is associated early astronomy, religion, and mysticism. It is symbolic of both stars and humanity’s earliest attempts to understand and communicate the order and unity inherent in Creation, nature’s rule.
Astrological Origins
The roots of the eight-point star symbol are in early astronomy. The eight lines are symbolic of the four corners of space (north, south, east, and west) and time (two solstices and two equinoxes.

An Italian nobleman named Pietro della Valle discovered the use of an eight-point star as a seal in the ruins of the ancient city of Ur (~2000BC), Tell al Muqayyar, in the mid-seventeenth century. He wrote “I found on the ground some pieces of black Marble…which seem to be a kind of Seal like what the Orientals use at this day: for their Seals are only letters or written words…Amongst the other letters I discovered in a short time was…a star of eight points…”
Abraham, the shared prophet of the monotheistic religions (Judaism, Christianity, and Islam) lived in the Sumerian city of Ur. Excavations from Ur reveal early use of the eight point star, often in the form of an eight petal rosette used in jewelry or metalwork decoratation.

The Sumerians used an arrangement of lines as a symbol for both star and God. The linear eight-point star represented the goddess Inanna, Sumerian queen of the heavens and Ishtar (Astarte), the Babylonian goddess known as “The Lightbringer.” An eight-point star enclosed within a circle was the symbol for the sun god. The “Babylonian star-cult is the core and the archetype of subsequent astrology.”  The Greeks recognized Venus as the morning and evening star is 400 BC, 1,500 years after Sumerians.

Venus is the morning star and the evening star: because it can be observed more clearly and longer than any other star, she could serve as guide, as point of orientation.The first star to be seen when the Moon shines, and the last star to remain visible when the Sun starts shining.Venus also has to do with traditions about their own origins: according to certain Essene traditions the Essenes came from Venus.  

Porta del Popolo

"In oggi questa è la Porta principale di Roma, non solamente perchè tra tutte le altre è la più magnifica, ma ancora perchè la maggior parte delle nazioni entra per essa, e per essa fanno l'ingresso pubblico gli Ambasciatori, e Cardinali quando vengono la prima volta in Roma, ed ancora i Re, e Regine, l'ultima delle quali fu Cristina Regina di Svezia in tempo di Alessandro VII. Chiamossi anticamente questa porta col medesimo nome della via Flaminia; ora però prende il nome dalla chiesa, che le sta accanto, o secondo altri da' pioppi del mausoleo di Augusto, che fin quì si distendevano, che populi diconsi in latino.
Tutto quel vasto sito, che da una parte è circondato da monti, e dall'altra dal Tevere, dicevasi anticamente Campo Marzio, perchè da Romolo dedicato a Marte, affinchè in esso si esercitasse la gioventù nell'arte militare, ed ancora per tenervi i comizi nell'elezione de' Magistrati; e però non era lecito ad alcuno abitarvi: vi furono bensì eretti fabbriche pubbliche molto magnifiche, cioè Circi, Naumachie, Teatri, Archi trionfali, Obelischi, Tempj, Portici, e Statue di uomini illustri senza numero: onde Aureliano, per non lasciar tante magnificenze esposte agl'insulti de' nemici, le incluse entro Roma, con distendere fin a quella parte le mura della Città. Fu rinnovata questa Porta per ordine di Pio IV. da Giacomo Barozio, ma con disegno del Buonarroti, e poi vi furono poste le due statue di s. Pietro, e di s. Paolo fatte dal Mochi; l'architettura però della parte dentro la Città è del Cav. Bernini."