Necropolis, of course, means 'city of the dead'. I think you get that 'city' feeling in this kind of cemetery. We wandered for a while, looking at the tombstones and the floral displays that families had left. It's kind of a comforting place really.
In New Orleans some years ago, we were told the cemeteries were built above ground because the water table was so high. But I've seen cemeteries like this all over the French Caribbean as well as France, so I wonder if it wasn't just tradition after all. And if that tradition dates back to the Romans, at least.