HOW THE GOLDEN HOUSE SURVIVED UNDERGROUND. It seems to me that the Golden House may have survived in part because of its excesses. The emperors that followed Nero were eager to wipe out all traces of it by filling it with earth and then covering it with more earth. This wikipedia entry on the Golden House describes the magnificence of the Golden House and how it came to be completely obliterated within 40 years of Nero’s death. The vaulted interior was filled with earth and the building was covered with more earth, providing a level surface upon which the Temple of Venus and Rome and the massive public baths of the emperors Titus and Trajan were constructed—and further sealed off the excesses of the Golden House.
The earth protected much of the building from vandals and “ensured the wallpaintings’ survival by protecting them from dampness”.