Contrary to many misconceptions, much of New Orleans' history remains intact, despite the devastation wrought by Katrina. Many of the famous above-ground cemeteries, for instance, are in reasonably good shape, including St. Louis Cemetery No. 3, which we visited on a tour arranged by Tulane. (I've just been visiting cemetery websites and learned that under no circumstance should anyone consider a solo visit to a New Orleans cemetery. Good thing I didn't let my natural affinity for cemeteries worldwide lure me back for a private walk. I had no plans to move in permanently.)
The cemeteries are above-ground for a couple of reasons. The more dramatically appealing has to do with New Orleans' location below sea level, which means that coffins buried underground have a tendency to pop back up during a flood or hurricane. A less dramatic but more likely reason is that above-ground burial was common in France and Spain, the two countries from which many of New Orleans' European residents arrived pre-1800.
For whatever reason, above-ground burial is emminently practical in New Orleans. Although numbers of names frequently appear on the tombs , they usually represent more former than present occupants. There are, after all, only two slots in most of the tombs, each of them usually owned by the same family for decades. The recently departed are buried in wooden coffins, and the intense Louisiana heat causes body and encasement to disintegrate rather quickly, enabling them to be swept into an opening in the floor of the tomb. Cremation in lieu of burial was not permitted by the Catholic church until recently, but "natural" cremation was acceptable.
You can see in the bottom photograph that the tombs are constructed simply, with only one layer of bricks needing to be removed in order to brush away a former occupant in order to install a new set of remains. (The photograph above that portrays the tomb of a Carmelite house of nuns -- many names but few spaces.)
New Orleans law still requires that a body remain in his or her original space for a year and a day -- a carryover from the years of yellow fever epidemics, when people did not know the origins of the disease and feared that the fumes from a decomposing body might be contagious if a tomb were opened too soon.
The tombs are more or less elaborate depending upon the income and status of the owner-families. The walls of the cemeteries contain the budget-rate vaults; the families with wealth produce elbaorate carving and statuary. The cemeteries are immensely interesting, with their lengthy litanies of French names and their village-like quality -- but apparently an official cemetery tour is the only safe way to go.