AN UNFINISHED PROJECT
The area today named the Underground Chamber now looks very different from how the Prince of Sansevero originally envisaged it. He conceived it as a small funerary temple for his descendants, half above and half beneath the level of the main nave of the Chapel. For reasons unknown, however, the project was never finished by Raimondo di Sangro or his heirs.
In a few letters addressed to the Academician of the Crusca, Giovanni Giraldi, and to the physicist Jean-Antoine Nollet, the Prince describes his design in detail. The oval temple (the shape is still preserved) “will appear to be excavated from the rock, and will be well lit by a cupola, which shall have a number of windows”. It would have been “divided into eight arcades with the same number of columns”, and the arches would have housed the marble caskets of the bones of his descendants.