In the main chapel, the tomb compositions of the two first kings of Portugal are especially relevant: Dom Afonso Henriques to the Gospel (left side of the altar) and his son Dom Sancho I to the Epistle (right side of the altar).
The two tombs are part of a magnificent sculptural work by the French sculptor Nicolau de Chantereine.
The construction of the tombs, which house the first two kings of Portugal, dates back to 1520 and is Gothic in style with Renaissance and Manueline elements. It was around this time that King Dom Manuel I ordered the transfer of the mortal remains of Dom Afonso Henriques and Dom Sancho I from the burial chests in the central body of the church to the main chapel. The transfer of the mortal remains of the two kings took place in 1531.
To the Gospel (left side of the Altar) lies the epigraphed tomb of Dom Afonso Henriques, the founder of the Kingdom of Portugal. The tomb is surrounded by large altarpieces with statues of saints - in the upper central part we can observe the Shield of Portugal supported by angels and in the lateral niches are the figures of St. Christopher and St. Helena.
In the lower central part, below are Our Lady of the Assumption, sided by Angels and the Evangelists, St. Mark, and St. Luke, on the flanks are faceted pilasters decorated with medallions, niches, and statues of the 12 Apostles.
At the Epistle (right side of the Altar) lies, also on an epigraphed tomb, Dom Sancho I (second King of Portugal and son of Dom Afonso Henriques). As in the Tomb of Dom Afonso Henriques, in the upper central part, there is a sculpture of the Shield of Portugal supported by angels and flanked by St. John the Baptist and the Emperor Heraclitus or Constantine.
The tomb is surrounded by large altarpieces with statues of saints - in the lower central part are the images of Our Lady of the Milk, Saint Catherine and Saint Magdalene and of the Evangelists, Saint Matthew and Saint Luke, on the flanks are faceted pilasters decorated with medallions, niches and statues - of the four doctors of the church, the four cardinal virtues (Justice, Fortitude, Temperance and Prudence) and also the three theological virtues (Faith, Hope and Charity).
From the profuse decoration of the two tombs, the symbols of King Manuel I should be highlighted - the Armillary Sphere, the Cross of Christ, and the Royal Symbol - which affirm and reinforce the charisma of the royal power of King Manuel I.
«The "portals" lead the first two kings into the mythical sphere of the sacred by the enlightened hand of King Manuel I, "illuminated" by reason that legitimises his power, are clearly paralleled in the most paradigmatic work of his reign: the Hieronymites Monastery. »