The Basilica of St Patrick's Old Cathedral opened in 1815 as the seat of New York's first Catholic diocese, three decades before the Gothic Revival landmark on Fifth Avenue claimed its name. Beneath the sanctuary floor lies a labyrinth of brick-vaulted catacombs that served as the final resting place for more than 6,000 souls, including Pierre Toussaint, the Haitian-born philanthropist whose cause for sainthood advanced in 1997, and members of the Delmonico family, whose restaurants defined Gilded Age dining. The underground chambers were sealed to burials in 1852 when the city banned interments below Canal Street, transforming the catacombs from active necropolis into silent archive. Today the St Patrick's Cathedral NYC catacombs tour offers one of the few sanctioned descents into Manhattan's subterranean burial history. The 90-minute candlelit experience navigates passageways where limestone markers bear dates from the early republic, where cholera epidemics and yellow fever outbreaks left demographic scars visible in clustered burial years, and where immigrant families — Irish, Italian, German — secured plots in the only Catholic ground available in a city still wary of their faith. Above ground, the basilica itself carries the marks of two centuries: Federal-style brick facades that survived an 1866 nativist arson attack, Gothic windows added during an 1868 reconstruction, and a perimeter wall erected in the 1830s to deter grave robbers who supplied the city's medical schools. The catacombs' architecture reflects the spatial constraints of early 19th-century Manhattan. Vaulted brick ceilings rise barely six feet in some passages, forcing modern visitors to stoop where funeral processions once carried caskets by candlelight. Loculus niches line the walls in tiers, sealed with marble tablets inscribed in Latin, English, and occasionally French. The air remains cool year-round, a consequence of the chambers' depth and the thermal mass of surrounding earth. Restoration work completed in 2016 stabilized collapsing sections and installed discreet LED accent lighting, though guided tours still rely on handheld candles to preserve the sepulchral atmosphere. The site's location at 263 Mulberry Street anchors it within the historic corridor that once formed the heart of Catholic New York, before the archdiocese relocated its cathedral uptown in 1879. The old basilica became a parish church, its catacombs largely forgotten until the 21st century, when heritage tourism and renewed interest in the city's underground infrastructure brought visitors back below ground. Guided underground tours now depart Wednesday through Sunday, with each group limited to preserve the fragile environment and the solemnity a burial ground demands.