The present neo-Byzantine basilica, finished in 1924, sits over the tomb of Saint Martin and is a working pilgrimage site rather than a tourist monument. The interior is rich, dark, and mosaic-encrusted in a style that has aged unevenly, but the crypt — where Martin's relics lie under a marble slab — is genuinely affecting and quiet even when the upper church fills with visitors.
What is more interesting is what surrounds it. The medieval pilgrimage church that once stood here was one of the largest in France: an enormous Romanesque structure that stretched east across what are now Rue des Halles and Rue Descartes. Two surviving stumps mark the original footprint — the Tour Charlemagne to the north and the Tour de l'Horloge a block south. Walking between them gives you a sense of the scale of what was lost.