The cathedral's own name for the relic is the Holy Chalice (Santo Cáliz). The Holy Grail of medieval romance is a literary subject that first appears in writing in the late twelfth century.
The upper cup is polished agate, which the cathedral, following a study of 1960, dates to the second or first century before Christ. The jewelled gold mount is medieval, and the foot is a second agate vessel that the cathedral describes as Islamic work. According to the cathedral, only the upper cup is the relic.
Tradition says that St. Peter took the cup to Rome and that in the third century St. Lawrence sent it to Huesca in Spain, after which it was hidden in the Pyrenees. The cathedral introduces this account with the words 'Tradition tells us'. The oldest clear document is the act of September 1399.
The chalice is shown in the cathedral's former chapter house, a Gothic room built between 1365 and 1369 and now called the Chapel of the Holy Chalice. The chapel is part of the cathedral's ticketed cultural visit, so anyone who visits the cathedral can stand before the cup.