The Domus Aurea, or Nero's Golden House, was opened for public tours in 1999, after many years of excavation and study. In fact, what you can tour right now is but a fraction of a fraction of Nero's original domicile, which once covered most of downtown Rome. The Roman emperors who succeeded him won lots of points with the citizens by filling in, destroying, or converting his home for public use. Hence, much of it is unrecoverable. Regardless, ALL of it is simply underground, as is the case of most ancient Roman ruins in the city. The historical way of dealing with old structures in this town was to . . . what else? . . . bury them with the rubble of demolished buildings and build new things on top of the pile.
If you'd like to see this bit of ancient life, you must book a reservation in advance. Limited numbers of visitors are let into the site, and people who came to the ticket booth off the street when we were there were told there were no more spots that day (we were there at 11:20am). The ticket is 12,000 lire ($6) and the necessary audio guide (unless you have a privately hired tour guide) is 3000 lire ($1.50). The Italian guide who will lead you through the site will only take you into the rooms of note and tell you which number room it is, and then wait for you to listen to your audio. They will give very little in the way of English information. While we were there, two of the rooms that the audio guide described were off-limits (you must remember that this site is an excavation-in-progress). The entire tour lasts 45 minutes and you are not allowed to lag behind the group or stay past the time when the guide leads you out. Be forewarned that it is COLD underground. You can see in my photo below that the guide at the entrance is wearing a parka. They all were! Take a sweater at least and a jacket if you can. Don't buy the Guide Book from the ticket booth until after you complete the tour, and then see if you still want it. Honestly, from all I'd read in the travel books before we went there, I expected much more. What we found were lots of empty rooms with sketchy bits of murals still visible.
I did learn lots of interesting facts from the audio guide, though, like the term "grotesque" came from the Renaissance artists who would climb through openings to the Domus Aurea where they studied the frescoes and architecture of this "grotto" (they likened it to a cave).
I think this tour would be most interesting to serious students of classical culture, history, and architecture. Probably not of interest to children or teenagers--pretty bare bones type of place.