While the original sculpture at Troyes has largely disappeared, the cathedral still has a large number of its original stained glass windows, installed from the 13th to 16th century, along with some windows incorporating sections of medieval glass, for a total of 1,600 square meters of stained glass. The windows illustrate vividly the evolution of stained glass in France, from the 13th-century windows, with their deeply-colored, thicker pieces of glass assembled like mosaics, to the 15th- and 16th-century windows, using silver stain and enamel painting to create the effects of shading and perspective similar to those of Renaissance painting.^[22]

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  The Apostles - Lower windows of the nave, (south side Bay 51) (14th century)
 
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  Saint Peter (south side-Bay 47) (14th century)
 
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  The Annunciation (south side Bay 47) (14th century)
 
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  Apostles - Upper windows of nave (Bay 51)
 
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  Sainte Catherine of Alexandria and Saint Maurice of Agaune (16th c.)
 
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  The Mystical Wine Press - Bay 49 (1625)

The nave has glass from a wide variety of periods and styles – sometimes in the same bay. Some of the oldest windows, from the end of the 13th and beginning of the 14th century, are in the lateral chapels. Most of these underwent considerable restoration in the 19th century.

Other bays were given new windows in the 16th and 17th centuries. Of these, some were designed by Linard Gontier, a prominent Troyes artist of the Renaissance. His most famous window in the cathedral is the "Mystical Wine Press", inspired by the prominence of the champagne from the region. It depicts Christ with grapevines sprouting from this chest, and a variety of scenes associating grapes and wine with the apostles.

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  Windows of the axis chapel of the apse, dedicated to the Virgin Mary (13th–19th c.)
 
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  The Flight to Egypt and Adoration of the Magi (13th century)
 
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  Musician in the Tree of Jesse window, 13th c. Chapel of Joan of Arc, (Bay 31)
 
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  Detail of 15th-century window (Bay 38)
 
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  King Philip II of France (Choir, Bay 52)
 
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  Powers of the Ecclesiastical hierarchy (Bishops and Kings) (Bay 52)
 
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  Upper windows of the choir (Bay 208); Parable of the Wise and Foolish Virgins

The choir and the ambulatory, to the east of the cathedral, still have much of their original stained glass. The oldest windows are in the radiating chapels on the east, some dating to 1200–1230. The higher windows and those of the triforium date to about 1235–40. Some of these windows are more recent, but include portions of the older original glass, which had not yet been installed at the time of the hurricane of 1228. While many of the lower windows were considerably modified, the upper windows of the choir are mostly in their original state.^[21]

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  Grisaille windows in the transept

The transept windows have a mixture of styles. The windows on the west are from the 14th century, while those on the east were replaced in the 16th century with windows with tracery of the Flamboyant Gothic style. The triforium windows on the west were made in the 19th century, while the triforium windows on the east include vestiges of restored 13th-century glass.^[23]

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  The west rose window (partly hidden by organ)
 
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  Rose window of the north transept
 
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  Detail of the north rose window

The rose window at the west end of the nave, from 1239, was made by the artist Jean Soudain on the theme of the celestial court. The view of this window from the ground floor is largely obscured by the organ.

The rose window in the north transept, ten meters in diameter, was installed in the 15th century to replace the earlier window, which fell in 1340. It is in the Rayonnant Gothic style, with its tracery radiating outward from the center. The rose window on the south transept is a copy of the north window.

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  The grand organ, made in 1730 for Clairvaux Abbey
 
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  The choir organ

The grand organ is located on a tribune over the portal on the reverse side of the west front. It was originally built in 1730 for Clairvaux Abbey in Burgundy. When the abbey was closed in 1793 during the Revolution, the organ was nationalised and sold at auction. It was purchased by the overseers of Troyes Cathedral, but was not put into place until 1808. It replaced the original Troyes organ, built in the 15th century and placed next to the choir. That organ had been destroyed in 1792. The installation of the new organ was controversial because it largely blocked the view of the west rose window from the nave and choir.^[24]

The organ has fifty-five jeux or sounds, played with four keyboards and a set of pedals. The instrument was classified as an historical monument in 1963, and the case in 1974.^[25] The organ is decorated with statues of angels and atlantes.

The cathedral has a second, smaller organ, which is located in the choir. This instrument was built in 1865 and was restored in 1987. It has thirteen jeux, played with two keyboards and a set of pedals.

Troyes Cathedral has four bourdons, heavy bells which made a deep note, for tolling on solemn occasions. Each has a name, and all were made in the early 19th century, replacing the early bells taken out and melted down during the French Revolution.

• Petrus Carolus - (4500 kilos, made in 1827)
• Paulus Ana - (3,269 kilos, made in 1813)
• Savinianus - (2,437 kilos, made in 1813)
• Marie - (2000 kilos, made in 1827)

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  The Coffret of Troyes (Ivory, 11th century)
 
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  The Stuart Cross, made of crystal
 
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  Reliquary of Saint Bernard of Clairvaux, with silver, copper and enamel (12th century)

The treasury of the cathedral was constructed at the beginning of the 13th century within the choir, next to the apse. It was particularly designed to display the collection of sacred relics which the Bishop Garnier de Traînel had brought back to France from the Fourth Crusade. Some of the relics and other valuable objects were used as ransom for the captive King Francois I in 1525, and others were lost during the Revolution, but the collection was gradually rebuilt. It has a particularly large collection of medieval enamel art, made by local craftsmen in the 12th century, as well as vestments, reliquaries and other medieval liturgical objects. Notable objects include the coffret of Troyes, an ivory chest of Byzantine craftsmanship from the 11th century.^[26]

Among the stained-glass windows is one which appears to have a representation of the famous Indo-Parthian king Gondophares who was ruling in ancient Taxila from 20 to 41 CE, in what is now north-western Pakistan.^[27]

According to the legends and traditions contained in the Acts of Thomas, and preserved by the Indian Christians of St. Thomas, the Apostle Thomas fled to the East after the crucifixion. He stayed for some time at Gondophares' court where Thomas is said to have built a palace for him before heading on to southern India where he was, according to the legend, martyred near modern Chennai (Madras) ^[28]