I was lucky enough to visit in Nov 2003. You must make reservations at least 1 month in advance. Only 45 or so people get to go in per day in groups of 12-15. The Hypogeum is a massive underground series of carved out caverns that contained the remains of more than 7,000 humans. Some red faded rock painting remains. Recent research indicates that this site could be as much as 12,000 years old. The film and informative tour guides insure a thorough understanding of the site but no photos are allowed. They lock up your cameras! Not recommended for claustrophobiacs. The site is a 30 minute bus ride from Valletta. Be sure to visit the archaeological museum in Valletta to round out the experience.