this is the most fascinating documentary series I have seen in a long time. It is amazing the we can go where no man has gone before, for hundreds and sometimes thousands of years with 'access all areas'.
The reason I knocked off a star is that I found the rapid camerawork and fast cutting VERY annoying. And the presenter is so 'in your face' as he rapidly hurries around as if things are going to change in the next few minutes. This terrific programme is crying out for a Michael Palin or Tony Robinson to take control of the narration and do it properly. Also, and this is a big gripe, someone tell all American narrators that it is not "Edinboro" !!! As a Scot, I was horrified. Can they not do basic research ?
Camerawork and narration aside, this is a superb look into history and it is very hard not to watch it several times. Enjoy going underground and overlook the faults. Highly recommended.