Servatius was bishop of Tongeren in the fourth century, the first bishop to be buried on Dutch soil. From the moment of his death, objects associated with him became sacred by contact, and the chapter of his church spent the next thousand years collecting them. The treasury divides its survivors into four groups, but the most evocative are the so-called Servatiana, the personal attributes. A decorative silver key from the early ninth century, which legend says Saint Peter handed him in a vision. A silver-and-gold cross given by a duke of Bavaria, its wooden core hidden beneath enamel and gemstones. A green serpentine portable altar with silver ornaments, twelfth century, the kind of stone a traveling bishop would carry. And the cup, a small Roman vessel of millefiori glass made when Servatius himself would have been more than two centuries unborn, woven into his legend by people who believed he had drunk from it.

In 1579 Spanish troops under Alexander Farnese, Duke of Parma, sacked Maastricht. The original reliquary bust of Servatius, the one that for centuries had carried the saint's skull through the streets in procession, was largely destroyed in the violence. Then something unexpected happened: the duke who had ordered the sack also paid to replace what his soldiers had broken. The bust on display today was donated by Farnese himself, still containing the skull it was made to hold. A few steps away stands the Noodkist, an oak chest covered in gilded copper, enamel, and filigree, made around 1160. For eight centuries it has held the saint's other bones. During the seven-yearly Pilgrimage of the Relics, when tens of thousands of pilgrims fill Vrijthof square outside, these objects come out of the dim chapel and into the dwarf gallery overlooking the crowd, exactly as they did in the late Middle Ages.

The most fragile treasures here are also the most quietly astonishing. From 1989 to 1991, specialists from the Abegg-Stiftung in Riggisberg, Switzerland, painstakingly restored the basilica's textile collection. What they were handling included silks woven in seventh-century Constantinople, fragments from Egypt, weavings from Central Asia, and locally made materials from across the medieval Meuse-Rhine region. The so-called albe of Saint Servatius and the robe of Monulph, his successor as bishop, are among the most important surviving examples of early medieval European textiles anywhere. Cloth normally rots within a generation. That any of this survived its first century is improbable; that it survived fourteen of them, through fires and floods and the storage habits of medieval canons, is something close to a miracle of attentive custody.

When French revolutionary armies took Maastricht in 1794, they treated the church as a bank. War taxes were demanded; canons paid with gold and silver. Chalices, patens, monstrances, anything that could be weighed and melted, went into the crucible. In 1798 the chapter itself was dissolved. A handful of pieces had been smuggled to safety by individual canons, and some came back when worship resumed in 1804, but many never did. Today, walking through the treasury, you stand inside the eleventh-century double chapel where Provost Humbert kept the relics from 1086 onward, with his own funeral cross now on display in the basement among the archaeological finds. The treasury is far smaller than it once was. What remains has the weight of nine centuries of curatorship, made heavier by everything no longer there.