In the poem, Paradise is depicted as a series of concentric spheres surrounding the Earth, consisting of the Moon, Mercury, Venus, the Sun, Mars, Jupiter, Saturn, the Fixed Stars, the Primum Mobile and finally, the Empyrean.

The Paradiso begins at the top of Mount Purgatory, called the Earthly Paradise (i.e. the Garden of Eden), at noon on Wednesday, March 30 (or April 13), 1300, following Easter Sunday.

Dante's nine spheres of Heaven are the Moon, Mercury, Venus, the Sun, Mars, Jupiter, Saturn, the Fixed Stars, and the Primum Mobile.

The next four are associated with positive examples of Prudence, Fortitude, Justice, and Temperance; while Faith, Hope, and Love appear together in the eighth sphere.

When visiting the Moon, Beatrice explains to Dante the reasons for the markings on its surface, describing a simple scientific experiment in optics.

They also meet Constance of Sicily, who (Dante believes) was forcibly removed from a convent to marry Henry VI (Canto III).

Justinian recounts the history of the Roman Empire, mentioning, among others, Julius Caesar and Cleopatra; and bemoans the present state of Italy, given the conflict between Guelphs and Ghibellines, and the involvement of the "yellow lilies" of France[11] (Canto VI): For some oppose the universal emblem with yellow lilies; others claim that emblem for party: it is hard to see who is worse.

The planet Venus (the Morning and Evening Star) is traditionally associated with the Goddess of Love, and so Dante makes this the planet of the lovers, who were deficient in the virtue of temperance (Canto VIII): The world, when still in peril, thought that, wheeling, in the third epicycle, Cyprian the fair sent down her rays of frenzied love,

[13] Dante meets Charles Martel of Anjou, who was known to him,[14] and who points out that a properly functioning society requires people of many different kinds.

[15] The troubadour Folquet de Marseilles speaks of the temptations of love, and points out that (as was believed at the time) the cone of the Earth's shadow just touches the sphere of Venus.

He condemns the city of Florence (planted, he says, by Satan) for producing that "damned flower" (the florin) which is responsible for the corruption of the Church, and he criticises the clergy for their focus on money, rather than on Scripture and the writings of the Church Fathers (Canto IX): Your city, which was planted by that one who was the first to turn against his Maker, the one whose envy cost us many tears

Thomas Aquinas recounts the life of St. Francis of Assisi, and his love for "Lady Poverty" (Canto XI): Between Topino's stream and that which flows down from the hill the blessed Ubaldo chose, from a high peak there hangs a fertile slope;

[18] Twelve new bright lights appear, one of which is St. Bonaventure, a Franciscan, who recounts the life of St. Dominic, founder of the order to which Aquinas belonged.

[21] The millions of sparks of light that are the souls of these warriors form a Greek cross on the planet Mars, and Dante compares this cross to the Milky Way (Canto XIV): As, graced with lesser and with larger lights between the poles of the world, the Galaxy gleams so that even sages are perplexed;

[24] Cacciaguida praises the twelfth-century Republic of Florence, and bemoans the way in which the city has declined since those days (Cantos XV and XVI).

[25] Finally, Dante sees some other warriors of the Faith, such as Joshua, Judas Maccabeus, Charlemagne, Roland, and Godfrey of Bouillon (Canto XVIII).

[27] The souls here spell out the Latin for "Love justice, ye that judge the earth", after which the final "M" of that sentence is transformed into the shape of a giant imperial eagle[27] (Canto XVIII): DILIGITE IUSTITIAM were the verb and noun that first appeared in that depiction; QUI IUDICATIS TERRAM followed after.

[28] Present in this sphere are David, Hezekiah, Constantine, and William II of Sicily, as well as two pagans: Trajan (converted to Christianity according to a medieval legend) and (to Dante's amazement) Ripheus the Trojan, who was saved by the mercy of God in an act of predestination.

Dante uses this opportune moment in front of the eagle to ask about the accessibility of Heaven to people who were born before Christ or lived in an area where Christianity was not taught.

Dante starts his question by positing such a person (Canto XIX): A man is born on the banks of the Indus, and no one is there to speak of Christ to read or write of him,

To answer Dante's question, the eagle says (Canto XIX): To this kingdom no one has ever risen who did not believe in Christ, either before or after he was nailed to the wood.

Beatrice, who represents theology, becomes increasingly lovely here, indicating the contemplative's closer insight into the truth of God: She did not smile.

In his reply, Dante refers back to the concept of "twisted love" discussed in the Purgatorio[44] (Canto XXVI): Thus I began again: My charity results from all those things whose bite can bring the heart to turn to God; the world's existence

St. Peter then denounces Pope Boniface VIII in very strong terms, and says that, in his eyes, the Papal See stands empty (Canto XXVII).

Beatrice explains the creation of the universe, and the role of the angels, ending with a forceful criticism of the preachers of the day (Canto XXIX): Christ did not say to his first company: 'Go, and preach idle stories to the world'; but he gave them the teaching that is truth,

Dante sees an enormous rose, symbolising divine love,[49] the petals of which are the enthroned souls of the faithful (both those of the Old Testament and those of the New).

(The Empyrean as a whole abounds in Marian elements, such as the canto number 32's digits' adding up to five, which may represent Mary because of her five-letter name in Italian—Maria—and her experiences' having notably come in sets of five.

In late medieval Italy, poets such as Jacopone da Todi wrote praises of Mary called laude, and Dante's prayer to the Virgin takes inspiration from this tradition and condenses its form, focusing first on Mary's role on Earth and then her role in Heaven and her motherly qualities.

God appears as three equally large circles occupying the same space, representing the Father, the Son, and the Holy Spirit.