The Camino is the most successful pilgrimage revival in the modern world. What sits at the end of it is a genuine archaeological puzzle wrapped in a legend that almost nobody defends literally.
The legend
James the Great, son of Zebedee, was executed in Judaea in about the year 44, the only apostolic martyrdom the New Testament actually narrates. The Compostela tradition holds that he had previously preached in Spain, and that after his death his body was carried by sea to Galicia and buried there.
There is no early evidence for any of it. No source before roughly the seventh century associates James with Spain, and the transport of the body is a later elaboration still. Mainstream scholarship, including Catholic scholarship, does not hold that James preached in Spain or that the remains at Compostela are his.
What is actually under the cathedral
This is the part usually left out, and it is the interesting part.
Excavations beneath the apse, begun in 1879 and resumed systematically in the twentieth century, found that the altar stands over a genuine late Roman and early Christian funerary complex: a small mausoleum of perhaps the first to third centuries, within a cemetery that remained in use into the Suevic and Visigothic periods, with burials around it.
So the ninth-century church was not built over nothing, and not over an invented spot. It was deliberately built to enclose a real, ancient, and evidently venerated Christian burial in a Galician wood.
What the ninth century did was identify that burial. Around 814 a hermit is said to have been led to the site by lights; the local bishop, Theodemir, declared it the apostle's tomb, and King Alfonso II built a church over it. Theodemir's own grave was found beside the site in 1955, with an inscription, which confirms the ninth-century account of the discovery even as it says nothing about whose tomb was found.
The most defensible position: an ancient Christian burial of some local importance, correctly recognised as ancient and important, and then given a name it probably did not have. That is a misidentification of something real, which is a different order of thing from a fabrication.
The relics, lost and found
The remains were hidden in 1589 against a feared raid by Francis Drake, and the hiding place was subsequently forgotten, for nearly three hundred years. They were rediscovered in 1879 and declared authentic by Leo XIII in the bull Deus Omnipotens of 1884. That was an ecclesiastical judgement, delivered on the evidence available to a nineteenth-century commission, and should be read as such.
The revival
The modern Camino is a genuine phenomenon and not a heritage exercise. From a few hundred people a year collecting the compostela in the early 1980s, the annual figure has passed half a million.
What is unusual is the composition. A substantial proportion of walkers state non-religious or mixed motives, and the church-run Pilgrim's Office records this without apparent embarrassment. The Camino has become a form that people who are not believers use anyway, which is either a dilution or a success depending on who is asked, and the cathedral has generally treated it as the latter.
At the Pilgrim's Mass the botafumeiro, a censer of some considerable weight, is swung on ropes across the transept by a team of men until it travels at the height of the vaults. The practical explanation usually offered, that it was to fumigate a church full of people who had walked several hundred miles, is probably true and is certainly plausible.
A Holy Year falls whenever 25 July, the feast of James, is a Sunday. The next is 2027.