The new staircase leads the visitor to the first floor of the arcade and the spaces of the new treasury, with the exhibition from the Loreto treasure. This collection of superb decorative artworks is, in addition to the treasure of St Vitus Cathedral, the only one of its type preserved in the republic.

The most valuable piece, in both material and artistic terms, is the famous Diamond Monstrance, made between 1696-99 in the Viennese workshops of J. B. Khünischbauer and M. Stegner. The 6,222 diamonds decorating this treasure were from the bequest of Countess Ludmila Eva Frances Kolowrat. This treasure is rarely used in the liturgy today, only for very exceptional occasions. The last time that pilgrims were able to venerate the Body of Christ, exposed in the gloriole of shining diamonds, was during a celebration in the autumn of 1999, 400 years after the arrival of the first Capuchins in Bohemia.

The sole Late Medieval work in the treasury is the silver gilded chalice, with the date 1510 on the stem. This anonymous work is decorated with a combined technique; judging by the formal arrangement and the selection of saints used in the decoration, it is most likely a Bohemian work. The basket (the actual body of the vessel) has six fields of alternately blue and red enamel with linear half-figures of the saints, Suffering Christ and the Virgin Mary; on the six-lobed base there are relief, cast and finely chased half-figures. It cannot be ruled out that this chalice, which Christoph Ferdinand Popel Baronet von Lobkowitz gave to the Loreto in 1654, originally came from the treasury of St Vitus.

One of the most valuable pieces of the collection is the domestic altar made of ebony wood, with a silver figural group of the Nativity of Our Lord. The Bethlehem scene is set in the precise portal architecture, with a series of silver miniature additions. The extension is decorated with silver sculptures of the Pieta and Christ as the Salvator Mundi. The work is marked with the coat-of-arms of the Mollart family, from which Maria, married to Adam Gallus Popel von Lobkowitz, the mother of Benigna Katharina von Lobkowitz, was descended. It is thus very likely that the altar, as a family treasure, was donated to the Loreto by the founder. The work bears the Augsburg mark AL and was clearly made by the goldsmith Abraham Lotter the Younger, documented in Augsburg between 1618-1625. (Comparable works have been preserved in the treasury of the Residence at Munich.)