We did have this on our radar but weren't entirely sure we'd squeeze it into our schedules. Our Vespa tour guide told us it was a good way to kill some time, and interesting to boot, so we made it a point to get there.
When we stopped by, we didn't know that reservations were highly encouraged. The nice lady at the front was able to get us in that afternoon, but she did say that "next time" we'll want to make a reservation online.
It's a quick stop, and worth the €4 entry fee per person. I wouldn't plan on spending too much time in here, and if you're prone to claustrophobia, I would recommend passing, just due to the narrow walkways and steps. Ah, and you definitely have to be able to walk, as there's no accommodation for those who are differently-mobile.
It was interesting to see the history and the relics unearthed onsite, and it's much cooler down there (a bonus in the middle of a steamy August, for sure.) read more