The mausoleum exists because Trois-Rivières wanted its cathedral basement back. When Assumption Cathedral launched a renovation campaign in the 1960s, planners decided to convert the crypt into a community room. That meant finding a new resting place for the bishops entombed below the nave. Two options arose: build a new crypt underground, as Quebec City had done at the Notre-Dame Cathedral Basilica, or build an entirely new structure elsewhere. The desire to reclaim the cathedral's full basement settled the question. At the same time, the Saint-Michel cemetery -- opened in the early 1920s on land purchased by the parish of Immaculée-Conception in 1923 -- was undergoing a major redesign. Landscape architects Benoit Begin and Georges Daudelin had already planned a funeral chapel at the cemetery's center. The solution was elegant: combine the bishops' mausoleum with the planned chapel, creating a single monument that would anchor the entire cemetery.

Leclerc designed the monument as two interlocking volumes. The chapel rises in a slender semi-cone, its shape reminiscent of a sail straining skyward. Its west and north sides stand open, welcoming congregants, while the east wall allows only a small aperture. A skylight angled at 45 degrees pours light through the roof. The benches, made of wood and concrete, sit slightly below ground level, drawing worshippers subtly downward even as the roof soars above. A small rounded sacristy with vertically striated concrete -- a signature technique of Brutalist architecture -- anchors one side. Gargoyles brace the roof, channeling rainwater away from the structure. The mausoleum portion, by contrast, crouches low. Its thick walls create a dim penumbra around ten grey granite gravestones, each slightly inclined, illuminated only by horizontal skylights fitted with randomly arranged iron bars. Above the window wells, an inscription reads: 'Let eternal light shine on them.' The roof is formed from two thin hyperbolic paraboloid sails resting on a central beam and the walls -- a mathematical elegance hidden inside a monument to death.

Between the chapel and the mausoleum, a single cantilevered beam spans the gap -- a horizontal concrete plane with no visible support, giving the uncanny impression that it hangs in midair. This is not mere structural showmanship. The covered passageway beneath the beam creates a deliberate visual breakthrough: standing at the cemetery's main entrance, visitors can look straight through the monument to the calvary -- a grouping of four bronze figures installed in 1968 on the central axis. Leclerc had studied this sightline carefully, exploiting the perspective so that the monument frames rather than obstructs the cemetery's spiritual focal point. The entire composition speaks in contrasts that mirror Christian theology: the chapel's lightness against the mausoleum's mass, abundant light against deliberate shadow, upward momentum against earthbound restraint. The building embodies the dual symbolism of the soul's ascent and the body's entombment in raw concrete and empty air.

The mausoleum holds a special place in Jean-Claude Leclerc's career, alongside the Notre-Dame-du-Rosaire church in Fatima and the Trois-Rivières city hall. After visiting works by Le Corbusier and working in the studio of André Wogenscky, Leclerc entered what scholars call his Corbusian period. The mausoleum bears the fingerprints of that pilgrimage: its massive walls, concrete sail rooflines, and gargoyles recall Le Corbusier's Notre-Dame-du-Haut chapel at Ronchamp and the Sainte-Marie de La Tourette convent. Yet the monument received almost no critical attention for decades. Major surveys of twentieth-century Quebec architecture by Claude Bergeron and Laurent Lamy ignored it entirely. It was not until 1994 that architect Daniel Durand discussed the work in a Docomomo Quebec newsletter -- and even then, he misdated the construction to 1970. Official recognition finally came in 2007, when the City of Trois-Rivières designated the mausoleum a heritage building, followed by provincial classification in 2009.

Five of the six deceased bishops of the Diocese of Trois-Rivières rest inside the mausoleum. The first, Thomas Cooke, was born in Pointe-du-Lac in 1792, built five churches as a missionary priest in Caraquet, and was appointed the diocese's inaugural bishop in 1852 before dying in 1870. His successor, Louis-François Richer Laflèche, was an ultramontane firebrand who co-founded the Ile-à-la-Crosse mission in Western Canada, attended the First Vatican Council, and fought a ten-year battle over the creation of the Diocese of Nicolet. François-Xavier Cloutier steered the diocese through the devastating 1908 Trois-Rivières fire and the First World War. The last bishop buried here, Georges-Léon Pelletier, participated in the Second Vatican Council and personally oversaw the mausoleum's construction -- making him the rare church leader interred in a monument of his own commissioning. Surrounding the bishops, dozens of abbots and canons rest in the cemetery grounds, their lives spanning from the 1830s to the 2000s, each stone a chapter in the long story of Catholic Quebec.