Nero's Domus Aurea (Rome's underground)

I visited last year, after 30 years of waiting for it to be open (it was open sporadically but never when I was there), and it was fabulous. I forget where I got tickets (perhaps tickitaly), there is an official site online. You will receive a voucher almost immediately. Your guide probably will be an archeologist, architect, art historian or engineer. Hard hats are distributed at the entrance.

We are looking forward to visiting in June. http://www.revealedrome.com/2014/12/the-domus-aurea.html

This is the site to buy tickets. It's a little slow today, so be patient. If it doesn't work, try just etickets.coopculture.it and then scroll down to Domus Aurea. There are guided tours on Sat-Sun. It's a little hard to find because there's no signage, though it's only a short uphill walk from the Colosseum, so make sure you have directions. If you're going in warm weather, take a jacket, it's a little chilly . . . and humid. It's impressive and the guide was very good. Toward the end there's a virtual reality part that is just amazing. I'm glad I did it.

I saw this book for sale and flipped through it, looks like a great resource for off-the-beaten-path interesting places.

We visited it on our third trip to Rome last September and it was fantastic. As others have indicated, you need to reserve tickets on-line ahead of time. From what I hear, it books up fast. Make sure to book the tour in English. Definitely take a jacket. It was a hot day outside when we visited but very chilly inside. We really enjoyed our visit and our guide did a great job of helping us picture what the palace would have been like in its prime. The scale/size of the palace and grandeur must have been incredible in Nero's day. Enjoy.

I visited the Domus Aurea in 2015 and it was fantastic!! I am a huge archaeology buff and had wanted to see it for years. Just be aware that it is an open archaeological site, so while it is amazing and stunning, it is also damp and rather dark and not quite museum quality restoration yet. There were a couple guys on our tour who grumbled most of the way because it wasn't shiny and sparkly, so it was not a good use of their time. I, on the other hand, wanted to go again, and I will do so next time I'm in Rome. I wish I could go back and see it in its hey day, with all of the splendor and the people and the gardens! Enjoy!
If you want to see some of my pictures, they are here:
http://deborahinitaly.weebly.com/domus-aurea.html

Thank you all! I just ordered my tickets and can't wait. We love ancient history and enjoyed the Scavi tour last visit.

They've also recently added a 3D virtual reality piece to some of the rooms. You put on the 3D VR mask and you can look around the room and see it the way it was 2000 years ago. (And, yes, it's VERY chilly inside, unlike the Vatican Scavi tour, which is like a sauna.)