The above-ground tombs in the cemeteries of New Orleans are often referred to as "cities of the dead."
New Orleans has always respected the dead, but this isn't the reason the tombs are above ground. Early settlers in the area struggled with different methods to bury the dead. Burial plots are shallow in New Orleans because the water table is high. Dig a few feet down, and the grave becomes soggy, filling with water. The casket will literally float.
The early settlers tried by placing stones in and on top of coffins to weigh them down and keep them underground. Unfortunately, after a rainstorm, the rising water table would literally pop the airtight coffins out of the ground. To this day, unpredictable flooding still lifts an occasional coffin out of the ground in those areas generally considered safe from flooding and above the water table.