“Six feet under” has a couple of significant meanings for New Orleans, La.

More than half the city, much of which was developed on reclaimed swampland, lies several feet below sea level and is sinking at the rate of almost half an inch a year.

Consequently, the city’s historically high water table made difficult, if not impossible, the widespread implementation of the second meaning of the phrase. Any hole deeper than a few feet tended to flood with subterranean water. Anecdotes abound of coffins, interred at the traditional depth of 6 feet, floating back to the surface.

None of the attempted remedies — such as drilling holes in the airtight coffin or weighing it with rocks and sand — kept the dead from “rising again” and the townsfolk of centuries ago settled on the alternative of “burying” their dearly departed aboveground in tombs, vaults and mausolea.

New Orleans hosts 42 such “cities of the dead,” the oldest, St. Louis Cemetery No. 1, having been established in 1789. Many of the sites are noted for their architectural and cultural importance and several have been placed on the National Register of Historic Places. About 100,000 visitors a year arrive from around the world to partake in educational guided tours of the cemeteries.

Several of the cemeteries underwent phases of expansion as the original blocks of land were filled to capacity. New Orleans has had its share of lethally rough times, including floods, hurricanes, devastating fires and widespread outbreaks of yellow fever and cholera, and perhaps the most gruesome narrative about the cemeteries is how quickly and relentlessly they reached their census limit.

For example, during the city’s worst yellow fever epidemic in 1853, approximately 1,300 people succumbed to the disease each week. In August of that year, St. Patrick Cemetery No. 1 buried about 1,100 yellow fever victims without the opportunity to inter them in rows, leaving the landscape a disorganized repository of hastily prepared graves.

Oftentimes the vaults are used serially for the deceased, usually family members who subsequently pass away and are placed in the family tomb. Helped by the area’s torrid subtropical climate, corpses entombed aboveground undergo a steady decomposition likened to a “slow cremation.” Typically, within a year, only the bones remain.

According to tradition, one year and one day after burial — current ordinances set the time frame at two years — the bones could be swept down an opening in the floor, emptying the space for the next occupant. Names and dates would be added to a plaque or headstone to preserve the memories.

Each cemetery has a unique history, with varying permutations of demographics, culture, adaptation to prevailing circumstances and geographical fortuity.

St. Louis Cemetery No. 1, 2 and 3

In 1789, Cemetery No. 1 was rushed into existence by the city’s government to augment the already full original centrally located cemetery, which had recently been closed. The new cemetery was located outside the fortified city, within 40 yards of the Charity Hospital Property. Its location, which abutted marshy swampland, was preferred by medical professionals concerned about the spread of diseases. It was intended as a temporary site, but was made permanent later in the year.

The first burials were underground, but an 1803 city ordinance mandated that all subsequent interments occur aboveground.

The cemetery’s most famous denizens include Paul Morphy, the first world chess champion; Homer Plessy, plaintiff in the landmark 1896 U.S. Supreme Court case Plessy v. Ferguson; and Voodoo Queen Marie Laveau, beloved for her legendary altruism in treating the sick during yellow fever epidemics.

Actor Nicolas Cage purchased a plot at the cemetery and commissioned a 9-foot white pyramid bearing the cryptic Latin inscription, “Omnia Ab Uno” (“All From One”).

The cemetery served as a location for scenes from “The Cincinnati Kid” and “Easy Rider.”

Cemeteries No. 2 and 3 were opened in 1823 and 1854, respectively.

The St. Louis cemeteries can only be visited via an official tour by a licensed guide. Tickets are $25 for adults and $18 for children.

Lafayette Cemetery

Founded in 1833, the nondenominational, nonsegregated cemetery contains the graves of immigrants from more than 25 countries and natives of 26 states. It serves as the final resting place of Judge John Howard Ferguson, the defendant in Plessy v. Ferguson. The location inspired Anne Rice’s writings on The Mayfair Witches and Vampire Lestat’s tomb.

St. Roch Cemetery No. 1 and 2

St. Roch hosts a Gothic Revival chapel and a stunning mosaic of saints. The cemetery was established in 1874 to serve a German congregation. The chapel was widely hailed as a place of healing, prompting regular pilgrimages by those in ill health or seeking spiritual consolation.

St. Joseph Cemetery No. 1 and 2

Originally established to provide a final resting place for German families and supply income for a German orphan asylum, both cemeteries became overfilled within 20 years of their opening.

Holt Cemetery

Originally built for the city’s indigent population, 99% of its population is buried underground.

Metairie Cemetery

This oval-shaped cemetery was chartered in 1872 on a former race track. It houses 9,000 graves, including those of nine Louisiana state governors, seven New Orleans mayors, three Confederate generals, famed swing and blues bandleader and singer Louis Prima and restaurateurs of Popeye’s and Ruth’s Chris Steakhouse.

Greenwood Cemetery & Mausoleum

One of the city’s largest cemeteries, Greenwood contains 20,500 lots and still averages 1,000 interments per year. It was opened in 1852 by the Fireman’s Charitable and Benevolent Association. Its Confederate Monument contains the remains of more than 600 soldiers. For more information, visit nolacatholiccemeteries.org or experienceneworleans.com.