It was built in the 13th century to house the precious reliquary of the True Cross. Legend has it that a knight returning from the Crusade lost a fragment of the True Cross to his native parish in the village of the Hospital. The relic is found, repeatedly, shining in the nest of a magpie. The population sees in it the will of the sky to maintain the sacred object and a chapel is built for this purpose on the place of the tree and at the height of the nest.
The chapel was probably rebuilt in 1611, date engraved above the north gate.
The building spans a paved road, a rare and original arrangement that makes it unique. In the shape of a Latin cross oriented, it has two levels, a ground floor composed mainly of two crypts and a high chapel.
On the lower level, to the east, the crypt largely opened by a semicircular arch and lit by a small window, houses a virgin placed on an altar and remains of the old chapel of Saint-Just demolished in 1950.
To the west, a semicircular arch leads to a broken arch door, the only vestige of the old chapel; it opens on a dark chapel at the bottom of which was the primitive access to the high chapel. This staircase destroyed in the seventeenth century was replaced by two external staircases, north and south of the nave, allowing a better circulation of the numerous pilgrims.
The choir of the high chapel, separated from the nave by a wrought iron balustrade, is covered with an altarpiece composed of five finely carved panels dating from the 19th century attributed to the rector Tanguy. The panelled vault is painted blue and decorated with golden stars.