It is impossible to describe this site - an underground temple to the dead, built over 5000 years ago, dating from older than 3000 years BC - what??!! Yes. The preservation of this site is remarkable. The tour is extremely well done - only 10 people allowed in per hour, an audio guide timed to the path that you are on, lights in the site that light up coinciding with the audio portion. A guide makes sure you pass through safely, but all information comes from the audio guide. I am still in a bit of a state of shock over it's age and how well it is preserved - very hard to wrap your head around something this ancient.
As by now you have read, you have to book your entry months in advance, though I understand you can sometimes get lucky with a booking. We were visiting Malta on a Celebrity cruise, and we wanted to be sure to see the Hypogeum, and since we only had one day available to us, we booked very far in advance so that we would be sure to get a booking at the time that we needed. Getting to the Hypogeum from the cruise port was a bit tricky, but everyone in Malta is so nice - we eventually found the bus terminus and were told that either bus 81 or 82 would get us close to the Hypogeum. Once on the bus, a very kind fellow passenger told us where we needed to get off, as the map we had wasn't all that clear - he saw our confusion, and initiated the conversation, asking us what we were trying to find - so nice of him!
Go to this site, and be amazed. And if you have time, definitely plan a trip to the National Museum of Archaeology and see in person the statue which is fondly called "Sleeping Lady" which was found in one of the grave sites in the Hypogeum, dating back to 3100BC. No one really knows what she is supposed to represent, her purpose, but it is so very exciting to think that a culture from 3000BC was creating art like this. We unfortunately were not able to go to the Museum, but I purchased a souvenir copy of the statue at a gift shop! She is so similar to modern sculptures done by Botero, one must imagine that he was influenced by her mysterious grace.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.